If you have a large number of people working on your Github repository at once, and especially if you have multiple branches of your repository going, you may encounter Merge Conflicts.
Merge conflicts generally occur when multiple people make contradictory changes to the same parts of a file, for instance editing the same line of a file in two different ways, or deleting a file that someone else made changes to. Github is often able to handle these conflicts on its own, but sometimes they have to be resolved manually. For more details on resolving merge conflicts, see Github’s own documentation.