What does concealed carry mean?

I have been reading about concealed carry permits, I am thinking of getting one.

The question I can’t seem to find an answer to is what exactly does concealed carry mean?

Do different states have different descriptions for “concealed carry” , if I am licensed in one state and visit another, which states description of concealed carry do I need to follow?

1. Does concealed just mean you can’t see the weapon at that point?
2. If I have it in a holster in clear view, eg on my belt but without a shirt covering it.
3. If I don’t have a concealed carry license can I still move it from place to place in its case, eg in my car to the range or to the shop to be fixed?

Sorry for all the questions but I do think that getting a concealed carry permit isn’t something for me to enter into lightly so I am trying to find out as much as I can before I go ahead.