The Dealer or Button is the Yellow square is this picture and action moves clockwise from him.
The Red Squares indicate early position players, the Blue Middle positions (MP, MP2, MP3) and the Green Late positions (LP, LP2, LP3)
In a game, the Dealer will deal out the cards starting with the small blind and working clockwise.
After the deal, the first person to act is the UTG (under the gun) position, and then play moves around clockwise till the Big Blind.
After the flop, turn and river, the action starts with the Small Blind and works clockwise ending with the Dealer.
It is generally accepted that the earlier positions require stronger starting hands to both play and raise as you have more people to act behind you