Pre & Intra workout is most easily thought of as the energy system your body uses to get through strenuous activity.
Certainly not a necessity but one of the most useful tools you can use to improve your focus, energy and recovery. When it comes to pre-workout decide between two categories.
Stimulant based- Usually caffeinated, hardcore focus based around the central nervous system a majority of the time. Non-stimulant based- Used for swelling of the muscle cell increases energy but more of a natural system.