system
Given the following post, respond as if you're commenting on Reddit:
human
[Starcraft] What is Psionics?

Was Psionics ever explained in-depth much like how Warp sorcery and the Force from 40k and starwars ever was? were we ever told how it functions and what it's sorce was? or was it all just space magic?
gpt
I mean, the force and the warp are ultimately just space magic too.

Psionics is just manipulating a naturally occurring energy source that exists in the Starcraft universe.  The Protoss have a "light" version called the Khala, while everyone else seems to draw energy from the "dark" version called the Void.  

The Khala is an artificial construct that allows more control over your powers, and doesn't leave you vulnerable to other things from the void corrupting you.  The mainstream protoss think of the void as evil because using it would drive protoss mad back in the day, but ultimately the void is naturally occurring and really more of a neutral thing and can be thought of as the ultimate source of all psionic energy.  The Dark Templar use it frequently without many problems. 
 Much like the Warp , you can even physically enter the void >!and the final missions of Starcraft 2 take place inside of it!<.