Was there a specific item in Disk Cleanup that you were wondering what would happen if you deleted it??
Clicking on the Clean up system files
button basically just restarts Disk Cleanup to have it "Run as administrator", and allows you to have the More Options
tab to delete more. Disk Cleanup - Open and Use EDIT:
Deleting these items will not hurt your computer. You would just need to decide if you wanted to delete them or not depending on if you wanted to keep them or not.