What is System Data and Why does take so much data storage space?

[AC Question]

I'm struggling to keep memory space. And haven't updated my photos app for this reason as well as other less needed apps. I wish to know why I shouldn't delete the system data on misc and why it takes so much memory space in the first place. Thank you. I believe I could guess to what this data is along with Cached data but I wish to know instead of just guessing.
If you need to know my phone is a LG G3, Model Number "GL-D855".

 

[belodion]

Welcome.

System Data probably refers to the OS or operating system, which you definitely must not delete.
Cached Data can be deleted safely. The G3 will remind you to do such things from time to time, because of LG's Smart Clean.