Discover credit card

So I’m 18 . I just got a discover card (yes I know it was a bad idea, but I’ve educated myself a lot on these) but I’m having trouble understand the difference between PAYING OFF YOUR CARD or MAKING PAYMENTS .. ? I just paid my transaction of $52 and I have another one waiting to be posted to my account for $113 soon as that hit my account I’m paying that .. but what’s PAYING OFF YOUR CREDIT CARD ? how do find how much I need to pay? They gave me a spending limit of $500.. Also I tried to pay OVER what I had to and they wouldn’t let me , it said I couldn’t go over $52