What is an upper/lower body split? An upper/lower body split is fairly self-explanatory, as it works the muscles in the upper body one day and then focuses on the legs and lower body muscle groups ...
TBH, it varies entirely. Most of whether you should stick to a workout split (i.e. doing upper body on a particular day, lower body on another and full body on another) comes down to your goal.
One of the major killers of muscle gains is overworking a particular muscle group and not allowing it enough time to effectively recover. The best push-pull-leg and upper/lower body workout splits ...