Bodybuilding fitness is about finding the most effective workout to build muscle. The 3-day split is one of the most effective because it allows you to hit each muscle group about 2 times a week if you go 5-6 days a week.
This will allow you to see maximum results when putting on muscle because you are tearing those muscles down and repairing them constantly.
This is also the hardest choice because they will be longer workouts because you will be working out more muscles than you would if you split up all the groups on different days.
This is also an effective if you only plan on going to the gym 3 days a week. Now you won't see results as fast but you still will see great results if you work hard every time you go to the gym and if your diet is under control.
The 3-day split is probably the most popular of the bodybuilding fitness because of the convenience of it. Most people have other responsibilities than just going to the gym and lifting weights.
This split allows them to workout their whole body within a week and see good results. Results will be slower but sometimes you have to make sacrifices due to other commitments such as a job or a family.
The answer is split up your body into 3 separate groups and rotate them. That's why it's called a 3-day split.
You don't have to do it like this but the way I have found that works best for most people is by splitting the body up as follows.
It's pretty self explanatory. You workout legs this day. That means you're focusing on calves, hamstrings, quads and glutes. I would aim to do a total of 5-6 excercises each time you workout legs.
You'll want to mix it up between isolation movements and compound movements to make sure you're getting a good workout.
Now that legs are out of the way we can focus on the upper body. Push day has to do with all the movements that involve pushing. So the muscles you will hit are Shoulders, Chest, and Triceps.
Same principle as legs, I would try to get a total of 5-6 exercises each push day. Switch it up every time and do different exercises depending on what you need to work on. Maybe some days you focus more on shoulders or more on chest. You're free to do what you feel like you need.
Now all that's left is Back, Traps and Biceps. These are all the major pulling muscles. The favorite day for most guys.
Same as the previous 2 days you want to focus on doing 5-6 separate exercises each day. This way you can see maximum results as well as switch it up every week.