The play is simple: You're dealt five cards. You decide which ones to keep by tapping the pictures on the screen or pressing buttons on the console. Then you hit the DRAW button and you get replacement cards for the cards you didn't keep. You win if you wind up with a traditional poker hand like two pair, straight, flush, etc. (We'll explain these below for those new to poker.) The amount you win per hand depends on the paytable of the machine you're playing. Here's a sample paytable.
Video poker is a very volatile game, about four times as much as blackjack. In any form of gambling, short-term results mostly depend on normal mathematical randomness (what some might call luck). However, in the long run, results mostly depend on skill. If you play a game with a return of 100.76% perfectly, that does not mean that you will have a 0.76% profit every time you play. The 100.76% is an EXPECTED return. Much in the same way, if you flip a coin ten million times, the expected number of tails will be five million, but it is unlikely you will hit five million on the nose. Actual results will vary significantly from expectations, but the more you play, the closer your actual return percentage will get to the expected return.