The term value bet refers to a situation when you are betting in a spot where you think you are ahead in the hand and want to build the pot to win more chips.
For example, let’s say you are playing in a$1/$2 cash game where you hit your flush on the river and decide to make a bet since you believe you have the best hand. This is a clear value bet because you want to get called by weaker holdings and try to build the pot to win more when your opponent calls.
It is also essential to understand how to size value bets properly so that you would get called often enough and get the most value in the long run. While there is no short answer to this, the most important factor to consider is your range and board texture and what hands you can represent with varying bet sizes.