"Le" and "La"
Le -> masculine
La -> feminine
L' -> followed by a word starting with a vowel or h+vowel
(watch out for "le lapain": it's a rabbit, not an androgynous bread ^^)
Yes. It definitely has to do with transgender but, you are right. Le is used mostly for males because it is masculine. La is followed for females because it's feminine. There are many questions regarding Le and La coming from myself also so I know it has to do with gender now.
I don't know which to use because on some questions, I get very very very mixed up, so I end up getting the question wrong.. any advice to tell which words are masculine and feminine?