Homogenised milk is processed milk, through heat and other forces, where the cream ends up blended in the milk, making a smoother milk. When I grew up, our milk was non homogenised and had a cream layer on top of the milk. This was all I knew and as a kid, I thought this was just luxury. I would actually get excited about a new bottle of milk so that I could put the cream layer on my cereal. You can still buy non homogenised milk but it is definitely hard to come by.
I make cheese at home fairly regularly and this always call for homogenised milk where the cream is already sitting within the milk.