The main reason that most people go to the gym is to gain muscle/strength and lose body fat, whether they are aware of it or not. This is sometimes described as 'toning up', 'getting fit', 'building lean mass' etc. They're all just synonyms for essentially the same thing, and the process that results in this happening is more or less the same as well.
The process is 1) get big and strong, and then 2) cut excess body fat. The problem is that many people think that they can