Tiles are small images designed in a way that they can be combined on a regular grid to produce bigger and varied images, so called tile maps.

A tile set (tile Sequence would be a more accurate term) is an ordered collection of tiles.

In the same way as an Indexed Image holds pixel indices at each position to determine the color of a pixel at that position by referencing that index in the Palette, a tile map holds indices which reference a tile in a tile set.

Unlike pixels, tiles can be non-rectangular, for example hexagonal or diamond shaped.

further reading:

• Tile-based Video Game
• Tiled Rendering