Anti: used when something is opposed to a particular practice, party, policy, action. "Anti" is used as "Against."
Multi: means many, lots or multiple.
1. This is an anti-virus software-- A software to protect your system against malicious software.
2. He is very good at multi-tasking. He can do many things at once.
multi-national-- a company which does business in many countries.
muti-tasking-- Doing two or more jobs at a time.
multi-vitamins-- A dietary supplement that contains all or most of the vitamins.
anti-terrosm- Defensive measures used to reduce the vulnerability (of properties or individuals) to terrorist act i.e to safeguard against terrorists.
anti-bacteria--A substance that destroys bacteria or suppresses their growth.
Student or Learner