Hopefully, this helps to explain gustar and encantar
In English, we commonly say "I like the dog" or "I love the dog." The English construction of this idea is "person - verb - subject."
In Spanish, there is no way in Spanish to say "I like" or "I love" in this way. (Saying "I love you" in a romantic sense uses different verbs, amar.) Instead, Spanish uses the verbs gustar and encantar.
To start with, gustar does not mean "to like." Gustar literally means "to please" as in "The dog pleases me." "A mi me gusta el perro" appears to use the same "person - verb - subject" construction as English "I like the dog." However, it literally translates to "To me - is pleasing - the dog" or "The dog pleases me."
Likewise, encantar does not mean "to love." Encantar literally means "to enchant" as in "The dog enchants me." "A mi me encanta el perro" appears to use the same "person - verb - subject" construction as English "I love the dog." However, it literally translates as "To me - is enchanting - the dog" or "The dog enchants me."
Good so far? Okay, now here comes a tricky part....
Because both gustar and encantar focus on what is being liked (rather than on the person who likes them) they conjugate according to what is being liked.
A mi me gusta el perro = The dog is pleasing to me = I like the dog
A mi me gustan los perros = The dogs are pleasing to me = I like the dogs
A mi me encanta el perro = The dog is enchanting to me = I love the dog
A mi me encantan los perros = The dogs are enchanting to me = I love the dogs
Still with me? Okay, now here's yet another tricky part....
Here's the construction:
Me gusta = I like
Nos gusta = We like
Te gusta = You (informal) like
Le gusta = He/she/you (formal) like
Les gusta: They / you (plural) like
A nostros nos gustan los perros = The dogs are pleasing to us = We like the dogs.
A ti te gusta el perro = The dog is pleasing to you = You like the dog
A ella le gusta el perro = The dog is pleasing to her = She likes the dog
A ellos les encantan los perros = The dogs are enchanting to them = They love the dogs
Because "me gusta" always means "I like" we generally drop the clarifying "a mi". If you use "a mi me gusta el perro" in Spanish it sounds like emphasis. As in how an American might say, "I don't know about you but I really like the dog." Instead, in Spanish we would generally use the simple form, "Me gusta el perro."
Same for nos gusta and te gusta.
However, you can see the problem with "le gusta" and "les gusta". Often the speaker needs to clarify just who "le" or "les" is referring to. So...
Me gusta el perro = I like the dog
Te gusta el perro = You like the dog
Le gusta el perro = [Who?] likes the dog? All you've told me is that someone [singular] likes the dog. I still don't know exactly who. Aunt Mary? A zombie? The neighbor's cat? Without context, I don't know.
Les gusta el perro = [Who?] like the dog. Same problem, just plural. Okay, great. Someone [plural] likes the dog. Who? My aunts? Zombies? All the cats? I don't know.
So we use "a [x]" to clarify and let us know exactly who likes the dog.
A mi padre le gusta el perro = To my father - is pleasing - the dog = The dog is pleasing to my father = My father likes the dog.
A mis padres les gusta le perro = To my parents - is pleasing - the dog = The dog is pleasing to my parents = My parents like the dog
~ And verbs? What if you like to do something? Always use the infinitive.
Me gusta tocar el piano = To me - is pleasing - to play - the piano = I like to play piano or I like playing the piano ~
Anyway, I hope this helps.
Be careful here - basketball / baloncesto happens to be an activity that requires "a". So it might properly be "Él juga al baloncesto." If you haven't already encountered it, there's a few long threads elsewhere of unhappy people pointing out this seeming inconsistency with DL.
The requirement to use "a" in this sentence is not tied to the word "baloncesto," but rather "jugar" triggers the use of the preposition "a." "Jugar" is one of a dozen or so verbs that require the preposition "a" to follow them.
So, if you are saying "He plays (or is playing) basketball," your translation will use the verb "jugar," which requires the preposition "a" before a noun or infinitive. Therefore, the Spanish translation would be, as you noted, "'Él juga al baloncesto." However, if you're saying "He practices (or is practicing) basketball," the Spanish translation is "Él practica el baloncesto," with no "a" inserted after the verb.
Here's a list of Spanish verbs that require the preposition "a" to follow them before a noun or infinitive: https://www.lawlessspanish.com/grammar/verbs/verbs-with-a/.
Thanks, but that's not what I was saying. In fact there is an apparent regionality to using "a" or not with jugar. Or so says this link. https://www.thoughtco.com/using-jugar-properly-3079752 My point is that DL should simply allow for some known alternatives like this.
Hopefully someone who understands and can explain grammar better will reply. But, for now...
"Le" is an indirect object pronoun = to/for it, him, her, formal you.
An indirect object tells you to whom or for whom something is done. An indirect object pronoun takes the place of an indirect object.
Your brother is the indirect object in the Spanish sentence in this exercise, "¿A tu hermano le gusta el baloncesto?" (The sentence literally says, "To your brother to him is basketball pleasing?") "Le" is the indirect object pronoun. "A tu hermano" clarifies who is being referred to by "le." (In English, we would normally use either the indirect object pronoun or the indirect object in a sentence, not both.)
"Does your brother like basketball?" ("brother" is the subject and "basketball" is the direct object.)
"Se" is a reflexive pronoun = to, from or for himself, herself, itself, yourself, themselves or yourselves
Some reflexive verbs already introduced by duoLingo: duchar, llamar, levantar
Reflexive verbs are used when the direct or indirect object of a sentence is the same as the subject. Reflexive verbs require the use of a reflexive pronoun to indicate who the subject/object is. These types of verbs are not very common in English, but are used frequently in Spanish to describe actions that a person does to, for, or from him or herself. Many verbs that express actions related to personal care or daily routines are reflexive and do not translate easily into English as "myself," "yourself," etc.
Spanish requires definite article for generic subjects. For example, to say "Dogs and cats do not get along" in Spanish, one would say "Los perros y los gatos no se llevan bien" because we are talking about dog and cats are in a generic sense. Let's use another example: "His favorite sport is tennis." is "Su deporte favorito es el tenis." in Spanish.
Gustar is a reflexive verb that almost always required use of the definite article for the subject of the sentence (in this case, baloncesto is the subject, so the definite article el is required.
Of course, if you were referring to a specific basketball, as in "the basketball you got for your birthday," you might say "el baloncesto..." or "la pelota de baloncesto."
The phrase A tu hermano is added to clarify who the indirect object le is.
Let's imagine two speakers in a conversation about basketball. If one person said, without context, ¿Le gusta el baloncesto?, the listener might not know who the le was referring to. To clarify, the initial speaker might initially say ¿A tu hermano le gusta el baloncesto?. Thereafter, if the two people continue to talk about the brother, they might omit the A tu hermano from their sentences.
Another reason that the speaker might at the A tu hermano is for emphasis. The speakers could be talking about basketball in general. One speaker might say, for example, My brother does not like basketball (A mi hermano no le gusta el baloncesto). But, then that speaker might ask the other person about THEIR brother, for emphasis, so the clarifying A tu hermano would be needed.