Permalink is a link in the Share menu of the https://www.openstreetmap.org map page (and also available for many other maps made with OpenLayers or Leaflet). A permalink URL is also visible all the time (uses a # symbol) in the address bar of your web browser. It is then possible to copy this link to be included in e-mails etc.
- the map position and
- also includes the currently selected style/layer of the map (Mapnik, Cycle, Transport, MapQuest Open).
Note: The style of permalinks changed in August 2013. Older style permalinks should still work.
For example this URL: https://www.openstreetmap.org/#map=18/51.45714/-0.20971 (pre-August 2013 style https://www.openstreetmap.org/?lat=51.457142&lon=-0.20971&zoom=18&layers=M ) ... presents East Putney in London. All the house numbers are shown in the Mapnik style
This URL: https://www.openstreetmap.org/#map=14/56.8139/-5.0650&layers=C (pre-August 2013 style https://www.openstreetmap.org/?lat=56.8139&lon=-5.065&zoom=14&layers=C ) ... specifies another location and a different layer URL parameter, to present the cyclemap, which shows topography and cycle routes.