The dealer is the player that has the button and he is the last one to act.
Player after dealer has to pay small blind to get cards.
The second player after the dealer have to pay big blind to get cards.
The dealer then hands out two cards to all the players, after this there is a betting round.
You can check, bet or fold.
The flop dealer puts 3 cards on the table these cards are community cards and all players can use them to get a five card poker hand.
After the flop there is one more betting round.
The turn the fourth community card and a betting round.
The river is the last card and it is now you want to have the best hand. After the river has hit the board it's a last betting round.
The best five card hand wins the pot.
After this the dealer button moves to the player that had to pay small blind and the game continues.
Starthand ranking for holdem is here.