What is difference between colonization and occupation of a country?

Colonization is the establishment of a settlement abroad controlled by the founding country.

Occupation is to take possession of a town or foreign country etc. by force. No establishment of a settlement is required and the country may still govern itself.

(Basic source: Chambers.)

That is largely a matter of perspective.

If you are from a wealthy nation that is profiting by stealing the resources of a poor nation, you are colonizing them.

If you are from a poor nation that is being controlled by military forces from a wealthy nation, you are being occupied.

It's the same as one man's freedom fighters are another man's terrorists.