A copy merge is basically where you take all of their changes.
Say you're in branch A and want to merge in branch B. Their might be conflicts, but you don't care, as you want whatever is in branch B. Almost as if you are copying from B to A.
Since you are in branch A, it is referred to as ours. Branch B is referred to as theirs. In git land, you can do this, assuming you are in branch A:
git merge -s recursive --strategy-option theirs B
This will merge, and take whatever B has as the word of Linus Torvalds.