An optimization process is a process that systematically comes up with solutions that are higher rather than lower relative to some ordering over outcomes; it hits small targets in a large search space, comes up with outcomes that you would not expect to see by random chance, atoms bumping up against each other with no direction or ordering at all. If an entity pushes reality into some state — across many contexts, not just by accident — then you could say it prefers that state.
Optimization is a very general notion that encompasses all kinds of order-generating processes other than emergence; optimization is about choosing or selecting outcomes defined as better.
Probably the optimization process you're most familiar with is that of human intelligence. Humans don't do things randomly: we have very specific goals and rearrange the world in specific ways to meet our goals. Consider the monitor on which you read these words. That monitor is a rather unlikely object to have come about by chance, and so of course, it didn't. Human economies over many years built up the infrastructure needed to build a monitor, and then built it, because people prefer to be able to see their files. It might not seem so impressive if you're used to it, but there's a lot of cognitive work that goes on behind the scenes....