What are junk files

[Skygazernana]

What is contained in junk files? What causes their creation?

 

[SpookDroid]

Usually their cached and temporary files. For instance, when you visit a webpage, the data it loads (images, etc.) has to be stored somewhere... but since chances are you're only visiting that specific content during a specific period of time, it is saved for future reference, but it will eventually be deleted (temporary files).

Apps also use a similar 'idea' when loading files into the system to help them work and load faster.