I think a good place to start your research is http://couchdb.apache.org/
They have an introduction, a technical overview, guides, a blog and a wiki.
An on http://www.couchbase.com/forums/ they have a dedicated forum. For your questions, that's a much better one than this forum.
can anyone help me concerning couchDB?
how to use it, does every server needs it installed in order for convergence?
after connection does it update automatically all servers if additional data is inserted???