- For the tag used for shops selling tiles, see Tag:shop=tiles.
Web maps work by loading map tiles from a tile server. Map rendering refers to the process of taking raw geospatial data and making a visual map from it.
There are two different types of tiles:
- raster tiles are just image files, that have already been rendered, for example: 
- vector tiles on the other hand contain geographic data that still has to be rendered
The www.openstreetmap.org homepage is using raster tiles.
Many renderers consult a stylesheet to decide how to display the content of the map. When using raster tiles, if you want to change the map style, you have to use a different set of tiles (often called a tile layer). Whereas with vector tiles, you can simply apply a different style to the same tiles (since the rendering happens on the client-side).
The tile layers featured by the www.openstreetmap.org homepage are described at Featured tile layers.
A tile provider is an online server that serves tiles via HTTP.
For providers of raster tiles, see Raster tile providers.
For providers of vector tiles, see Vector tiles#Providers.
Creating your own tiles
To create raster tiles you need a tile renderer.
To create vector tiles you can either generate them from OSM data or use a vector tile server to create vector tiles on the fly (from e.g. a PostGIS database).