After the preflop betting round, the dealer places three cards face-up on the table. This is called the flop, and it will give you more of an idea about the strength of your hand.
Following this is another round of betting. The preflop aggressor will usually follow through with another bet on the flop, since they showed strength by raising before the flop.
Did those three cards improve your situation, or did they ruin a good thing? As well, do you think your opponents are in better shape after the flop? Let’s say you raised on QQ and the flop comes 6h-2s-9d. It didn’t help you much, but how much good do you think it did the others? There’s no apparent straight or flush and if anyone has trips (three of a kind), you’ll find out soon enough. If you have to bet first, you probably should bet again and see what kind of a reaction you get. A continuation bet on the flop when you’ve raised before the flop will intimidate players with weak cards. Each time someone folds, your chance of winning the pot increases.