This is a question I get from more intermediate and advanced lifters, particularly friends. Not to say this isn't information for beginners, it just might be a little out of the realm of "necessary" at this point.
For those who don't know a "split" is how someone would break their exercises down for a week. For example, Lower Upper, Push Pull Legs, 3 Full body, 5 Full body, "Bro" splits, etc. Like most things in life, there is no perfect answer.
I recommend making a decision, pick one, and try it for at least a month. If it isn't stimulating your brain to want to continue then switch to something new. The program that is going to keep you showing up, is the one that is going to yield results 10 times out of 10. The split/program you actually enjoy will get you to show up more regularly.
One thing I would be remiss not to add is prioritizing rest. I try to remind people that we grow in recovery, not by constantly breaking down the muscles. As a couple good rules of thumb:
- Try not to exceed 16 sets per muscle group in a week. Limiting the amount of sets you do will force you to increase the intensity of your sets, while also preventing you from overtraining and causing injury. This will increase your progress and eliminate "junk volume".
- Every 2-3 days should be a day off the weights. Notice I didn't use "rest day". That's because a good cardio focused day, recovery/mobility day, or yoga session will vastly improve your weekly gains more than laying down on the couch watching football ever will.
- Enjoy the process! Going back to what I mentioned above, if you don't enjoy it, you won't show up. If consistency is the number 1 factor in losing weight or gaining muscle... showing up is the number 1 thing you can possibly do.