Page "GIS file formats" Paragraph 8

Raster data type consists of rows and columns of cells, with each cell storing a single value.

Raster data can be images ( raster images ) with each pixel ( or cell ) containing a color value.

Additional values recorded for each cell may be a discrete value, such as land use, a continuous value, such as temperature, or a null value if no data is available.

While a raster cell stores a single value, it can be extended by using raster bands to represent RGB ( red, green, blue ) colors, colormaps ( a mapping between a thematic code and RGB value ), or an extended attribute table with one row for each unique cell value.

The resolution of the raster data set is its cell width in ground units.