Just use that sheet to get used to the hands, it'll all start to become easy to know the best hands, it starts to make sense. Just play online with that sheet as reference and you'll pick it up. If you're thinking about taking it up for money, here's a little advice...
If you're thinking about doing it for money with your current experience level...don't. You might find this interesting...
And, do not play online, it's not poker. poker you have to be on a table looking at your opponents. Online too fast, no fun. EDIT: I'm talking after you've learnt the basics off the computer.
Every category is split into many levels of low-high, you and me can be straight flush, but mine can be higher than yours. So there many possibility, if many people plays, there can be 2 or 3 decks of cards used.
One deck of cards per game. You can have a room full of people all playing poker using many cards but they aren't all playing the same "game". You can go to the school grounds and watch many people playing basketball with many different balls and hoops but their is only one ball used in any one game.