What is Uproperty and how do you properly use it

Im doing the the C++ tutorials on the website and im at the do it your self part. I dont know how to use the Uproperty macro and I cant really find any documentation that can help me better understand it, can some one give me a plain English way f explaining what it is what it does and an example of how to use it?

I have found an answer and it was in this link: https://docs.unrealengine.com/latest/INT/Programming/Tutorials/VariablesTimersEvents/2/index.html

UProperties are described here: UProperty

Unfortunately, that link is dead now.

Check it here