Sprint
A fixed block of time, usually one or two weeks, in which a team commits to finishing a specific set of work.
What it tells you about a developer
A candidate who talks fluently about sprint planning and what did or did not fit has worked on a team with real delivery discipline. That kind of team usually finishes a consistent, predictable amount of work each sprint, and this candidate can point to what that number was.
Sprints are the core rhythm of most agile teams. At the start the team plans what fits. During the sprint developers work the agreed tickets. At the end the team demos what shipped and reflects on what to improve. The sprint boundary is what makes progress measurable week over week.