What is OpenStreetMap?
Simply Wikipedia for maps. OpenStreetMap (OSM) is a map that anyone can edit, similar to Wikipedia, but not the same. Everything you see in the world could be in one map. Open-source, usable for everyone. Wheelmap helps people with disabilities and Kurviger can show routes for motorcyclists that are more curvy and outside of residential areas. There are many more examples how the data you contribute is used (just scroll down).
How is it different from Google Maps?
Google Maps is great but not open data. Are you allowed to print it commercially? No. Can you take the map data and create your own routing engine? No. Create your own map style from their data? Nope. Google has invested a lot of money to get all those building shapes, lakes and other geographical information. They won’t share it and that’s their right. But we believe that all of this information should be available in one big database free for everyone.
Isn’t mapping complicated?
No. The world of OpenStreetMap consists of three basic [elements](http://wiki.openstreetmap.org/wiki/Elements). Points (nodes), lines (ways) and areas. They get their values through so called tags (like name=Golden Gate Bridge). For example a church could outlined as an area and tagged as:
name=Church of our Lady building=church amenity=place_of_worship religion=christian denomination=evangelical
We use nodes for shops, small features like fountains or bicycle repair stations. Ways for roads, paths, small waterways. Areas for forests, buildings and ponds like in the image below.
How can I start to edit?
We have two main editors for armchair mapping. iD and JOSM. JOSM is an advanced standalone editor, but it’s better to have some experience before you begin mapping with it. I will focus on the browser based one called iD, which has a great tutorial. Another good learning source is LearnOSM.
To show you how easily stuff can be added I made these three videos that explain how to add small things to OpenStreetMap.
To add things with your mobile phone you can use OsmAnd or Maps.me, which also displays the map you help to create. StreetComplete for Android is the perfect app to enhance informations to things that are already existing in OSM.
If you want to know where all these informations appear you should have a look at this article.