Each time a player bets in Poker, there's something they want to achieve by doing it. There are 3 main reasons to bet:
1) Value Bet: Extract more money from your opponent/s when you believe your hand is the best.
2) Bluff: Make your opponent/s fold because you believe your hand is winning.
3) Semi Bluff: Make your opponent/s fold, but it is not a disaster if our opponent calls because you still have a lot of outs to make what you believe could be a winning hand. It's worth noting that we can only semi-bluff if there is one or more community card to come.