Difference between "snälla" and "tack"
Duolingo will use both "tack" and "snälla" to mean "please". They will also use "tack så mycket" and "tack snälla" to mean "thank you so much" or "thanks so much". I'm wondering what the difference is, or if they are simply exact synonyms of each other. I am assuming there is some kind of nuanced difference between them because that would be kind of silly to have two words be exactly the same in every way
They are not synonyms. "Tack" is "thank you". "Snälla" literaly means "kind", "kindly", as in "Kindly open the door". "Tack snälla" is a bit of a special case, meaning something like "Thank you, kind [of you]". Compare with ideomatic English "So kind".
Thus, you can never say "thanks" without "tack". The problem with "please" is that it does not map exactly onto Swedish, so all translations are adaptations. The literal translation of the Swedish sentences would be along the lines of "Could you open the door, thanks?" or "Open the door, kindly", which sound a bit unusual in English.
a more proper ”please” would be ”är du snäll” or ”är du vänlig”. snälla sounds more like charming a family member to do something, snälla Karin kan du öppna dörren för mig? I can see a parent or a child saying that