How do I plot the points (data) from the database to the OpensStreetMap?

I wonder how the mapping thing works in the OpenStreetMap. I'm building an app that uses my own database(which I will build using OS开发者_C百科M dumps using Osmosis; same as in the OpenStreetMap website). I have really no idea how it works. Thanks in advance! :D

http://wiki.openstreetmap.org/wiki/Develop is your friend for these kind of answers. They explain (depening on the page) pretty detailed how things work.

I don't know how Osmosis does things since we are working with osm2pgsql but I assume they are almost similar: It basically looks for certain tags (since everything is "tagged" by the OSM community) and stores it in the database. So if you have a supermarket POI "some_supermarket" that has a tag "supermarket" an entry in the database will reflect these infos and the coordinates. Streets, buildings and so on are only coordinates that get connected when rendering or processing it.

If you ask for the rendering of the tiles/geo-images, there are renderes available that do these tasks. The wiki from above will give you lots of answers, just search for "renderer". They just retrieve the information (depenging on zoom level and your setting) from the database for a certain bounding box and interpret the data from the database e.g. the know that a street is connected and needs to be colored in grey.