You use proper to describe things that you consider to be real and satisfactory rather than inadequate in some way.

The proper thing is the one that is correct or most suitable.

If you say that a way of behaving is proper, you mean that it is considered socially acceptable and right.

You can add proper after a word to indicate that you are referring to the central and most important part of a place, event, or object and want to distinguish it from other things that are not regarded as being important or central to it.