Imagine taking a picture puzzle that you'd completed, putting it in your clothes dryer, and turning on the tumbler. I think you and I can both safely say that you'd get out a jumbled mess of pieces with little to no resemblance to the completed puzzle.

Now imagine taking a disassembled picture puzzle and putting it in your tumbler. You and I would both be very surprised if what came out was a correctly completed puzzle.

Mathematically, there is only one way that the pieces of the puzzle can all position themselves correctly to solve that puzzle. There are a huge number of ways those pieces can position themselves that don't solve the puzzle.

This is, mathematically, what is meant by "order" and "disorder." It means the system is in a configuration that is more– or less-constrained state.

A more classical version of this is to say that if you have a divided box with oxygen on one side and nitrogen on the other, this has a lower entropy than the same box where the oxygen and nitrogen are intermixed. Removing the divider from a box where they're separate will lead to them mixing, but removing the divider from a box where they're mixed will not lead to them separating. There are more configurations where the gases are mixed than where they are separate.

There are some subtleties when you look deeper at what it really means to be in a constrained state and how this interacts with quantum mechanics, but this is a reasonably accurate picture of how entropy works.