Acting last is a huge advantage because you have more information than someone who was forced to act earlier. Position is an advantage at all stages of the hand.
If you're in early position and bet on the flop, you have no idea what the players in later position are going to do. In contrast, if you're on the button post-flop you've seen what every other player's decision is going to be before you have to act.
Poker is a game of incomplete information and if you're playing from early position your information is even more incomplete. This is why charts and guides invariably say that you need a stronger hand to enter a pot in early position than you do in late position -
hands like AT/AJ or small pocket pairs are great to raise with from the button but are much more difficult to play from UTG, especially if your post-flop game is not strong.
In a scenario such as the one you outlined where you raised from an earlier position and got a call from a player in later position, you should consider whether it is appropriate to put in a continuation bet rather than just checking the flop and then check-raising. You always have to consider what your "story" looks like to the other player and what you are trying to make them think you have.
