What happens when I move or copy contact(s) from one group to another?

First, "copy" means you care copying a contact(s) from one group to another. This action will keep the contact(s) in both groups. 

What happens if a contact(s) is already in the group I am trying to move them to?
"Move" means you are moving them OUT of one group, and INTO another. 

If the contact(s) is already in the group you are trying to move them to, they will not be added again. They will not be in there two times. It will not move the contact(s) OUT of the group they are being moved from.  

For example, if you are moving 10 people from "group A" to "group B", and 3 of them are already in "group B", only the 7 that are not in "group B" will be moved. The other 3 will remain in "group A".