Conflict
In plain terms
When changes can't be automatically reconciled.
Going deeper
A conflict arises when version control can't merge competing changes to the same content and needs a human to resolve them. Two edits collide.
Under the hood
Common during merges/rebases on the same lines; resolved by editing conflict markers and re-committing.
Examples
Merge conflicts, rebase conflicts, simultaneous edits, resolution.
Think of it like...
Like two editors changing the same sentence differently, requiring a decision.