A raster data model uses a grid. One grid cell is one unit or holds one attribute. A cell can hold a number or an index value standing for an attribute. A cell has a resolution, given as the cell size in ground units. Points and lines in raster format have to move to a cell center.
Lines can become fat.
Areas may need separately coded edges. Each cell can be owned by only one feature. As data, all cells must be able to hold the maximum cell value. Rasters are easy to understand, easy to read and write, and easy to draw on the screen. Grids are poor at representing points, lines and areas, but good at surfaces.