There are two types of people you will see at the gym; one that are body builders and others that are power lifters.
The sole purpose of body building is maintaing a desirable amount of muscle while still being shredded and toned. Body builders have strict diets along with 5-7 meals per day to maintain a high metabolism, I will elaborators more on metabolism later but for now, remember that body builders have a goal of creating lean muscle with the lowest amount of body fat possible.
Next we have power lifters. These people are physically unattractive and don’t care about physique. Their main purpose is to solely pick up as much weight their body possibly can. These people will have goals such as curling and benching lots of pounds in one heavy set. Power lifter are very enthusiastic about increasing bench max.
I will elaborate more on both but for now get the bigger picture, body builders want to have a good body physique while power lifters want to lift higher weights.