In Texas Hold’em, the term preflop describes all the action that happens before the flop, i.e., before the first three community cards are dealt.
When you see a preflop poker hand chart, thus, you know that this is a chart telling you what poker hands to play before the flop, depending on your position at the table.
Preflop is one of the four betting streets in Texas Hold’em, followed by flop, turn, and river. It is arguably the most important street, though, as any mistakes you make during the preflop play can easily compound by the river, resulting in significant losses.