An edit war occurs when editors who disagree about some aspect of the content of a page repeatedly override each other's contributions, rather than try to resolve the disagreement by discussion.
Edit warring is unconstructive and creates animosity between editors, making it harder to reach a consensus as to the right way to improve the wiki.
What Edit warring is and what Edit warring is not
Situations will inevitably arise where editors have differing views about some aspect of a page's content. When this happens, editors are strongly encouraged to engage in civil discussion to reach a consensus, and not to try to force their own position by combative editing (making edits they know will be opposed) and repeated reverting.
Not every potentially controversial edit, and not every revert, is deprecated as edit warring.
The sanctions on two users edit warring is a warning, and if that fails, then a blocking.