You use reality to refer to real things or the real nature of things rather than imagined, invented, or theoretical ideas.

The reality of a situation is the truth about it, especially when it is unpleasant or difficult to deal with.

You say that something has become a reality when it actually exists or is actually happening.

You can use in reality to introduce a statement about the real nature of something, when it contrasts with something incorrect that has just been described.