Welcome to the world of PC building.
If you look at CPUs and GPUs, they will have power requirements/consumptions.
A CPU or GPU may have minimal power consumption/requirement at idle (like 13-14 watts). But depending on the applications (Gamers, Overclockers, Auto-CAD, 4K Video Editing) -- the power requirement of a CPU may be 100-200 Watts and GPUs may require 300 Watts or more.
Like the GeForce 2080S says "recommend 650W PSU".