Backup Vs. Back up
Backup can be a noun or adjective while back up can be used as a verb.
"Where did you put the backup file?" (Adjective)
"Where did you put the backup?" (Noun)
"Did you back up the files?" (Verb) (It is written as two words.)
"Did you clean up your room?" (verb)
"There is a cleanup today." (noun)