A merge conflict occurs when a version-control merging operation cannot automatically reconcile changes under its merge rules. For a typical three-way merge, the tool compares two revisions with their common base. Incompatible edits to the same region, or deletion on one side and modification on the other, can require a human decision.[ref]
git-merge in the Git documentation. True merge, How conflicts are presented and How to resolve conflicts
For example, the base contains
threshold=5; one side changes it to 7 and the other to 9. Choosing either value or a new value requires understanding the intended behavior. After editing the combined result, the resolver records that decision in version control. A textually conflict-free merge can still break a function's contract, so successful automatic combination supplies weaker evidence than software testing of the integrated program. New to topics? Read the docs here!