Level design is the process of creating playable content that serves as a medium of delivering gameplay and storytelling experiences to players. Some games rely on carefully crafted and strictly planned levels/maps/stages/missions. Others leave room for randomization, but still require human input to create puzzles, challenges, enemy spawn rules, pre-assembled level chunks, and even high-level world-building rules.
The craft of level design lives on a flexible cross-section between game design, storytelling, and art. Depending on the needs of the project and team structure, a level designer will either take care of the entire level design from start to finish or ask for artistic input from environmental artists, who'll take care of the visual side of things for them. In smaller teams, it's quite common to have a generalist game designer tackle level...
