"La" is used for female words and "Le" is used for male words. In french every noun is either male or female, there is no "it" in French. You need to learn whether a word is male or female or there may be some tricks online to know whether a word is male or female.
"La" is mainly used for words that end in "e" ONLY. These are know as feminine . "Le" is used for words that end in any other letter. These are known as masculine. However, there are some exceptions that don't follow these rules but those are rare.
An apostrophe replaces a vowel only when the next word begins with a letter. It sounds smoother. For example, "l'oiseau," "l'art," etc. Because "vin" begins with a consonant and not a vowel, its article is "le".
Don't forget that 'h's are silent in French and so there will be an apostrophe before an 'h' too, l'homme etc.
The l' is only used for words that start with a vowel. Vin stars with a "v" and therefore it is "le vin". If the word was "eau" for instance (water), it would be "l'eau" because it begins with a vowel and wouldn't look right it it was "le eau" or "la eau".