WHAT IS SYSTEMUISERVER?

Can someone give me a basic quick rundown of what exactly "SystemUIServer" is and what it's controlling?

I have just now come across this while going through my security and privacy preferences... I have ZERO knowledge of my MacBook pro's software.I only basic programs.

I am shrewd and clever for most topics of interest, but I'll be the first to admit that even after spending 30 minutes researching the "SystemUIServer" ([I don't have enough basic knowledge to understand the IN DEPTH information that I've read])

I would appreciate any help that could be explained as if I know nothing of the subject.

Even the most basic of understandings would help me... thanks a lot and I hope someone out there can dumb this down for me!