There are several ways of using lSM to simply view the map or to view the data contained within. You can use lSM irrespective of the device or the operating system that you have.
In the browser: Simply visit http:// openstreetmap.org (or osm.org). You can change the base map by clicking on the little drop-down box at the top right-hand side of the map, and choosing a map (from Cycle Map, Transport Map or the Mapquest lpen Map). When viewing the map, aerial imagery is not available, due to licence restrictions (or it won’t be free, so get over it).
After you zoom into the map to a reasonable level, you can view the map data by clicking on the drop-down arrow adjacent to the Edit link above the map. It is also possible to export the map data as XML, or an image, by clicking on Export. This way, you can download parts of the map to make roughly printed-out paper maps.
On your Android device: For Android, there’s an excellent application called lSMAnd. You can download it either from the Play Store or from the F-Droid application for Android.