What is a fag?????? plz tell me!!!!!!!!!!!!!!!!!!!!!!!!?

ppl at my college have been calling ppl fags and i just dont know wt it is dont call me dumb beacuse idk wt it is . but when i was young my parents never swore in the house and they sent me to private skewl all my friends were straght a students like me and we played educational games!! we neva swore!!! and ik every other swear exept a fag..... wt is it plz explain it !!