When do you use the expression a la?

Okay so a la is the feminine form of the definite article.

So when your gonna going somewhere  and the place is femine you use it.

for example: Yo voy A LA casa de mi amigo

your going to the house off your friend house (casa) is femine,  

another example:¿ tu vas a ir a la fiesta ?

your going to party?

a la means to but in femine

a el is masculine

Explanation: