I don't know what letdown even means...

Ti

I feel so stupid asking this, but I have no clue what some of the lingo means... I hear people talking about letdown, hindmilk, for milk..... It's honestly starting to scare me away from trying to breastfeed, I mean if I don't know what the terms mean, how the hell am I EVER gonna be successful feeding my baby girl... I know how to mix formula and water, and have nooo special terms to confuse me!!!! Help!!!!!