Meaning: Do something that should have been done earlier
Example: I'm going home to CATCH UP WITH my sleep.
Meaning: Meet someone after a period of time and find out what they have been doing
Example: I CAUGHT UP WITH her at the conference.
Meaning: When something negative starts to have an effect
Example: His criminal behaviour is starting to CATCH UP WITH him.
Meaning: Punish someone after they have been doing something wrong for a long time
Example: The tax authorities CAUGHT UP WITH me for not submitting my tax returns.
Meaning: Learn something new that many people already understand
Example: My mother's trying to CATCH UP WITH computers.