I'm beginner in Sharepoint 2010. I would like to develop a solution with Sharepoint (interaction with api Linkedin or google maps).
I see many samples but the hierarchy of the vs project is unclear. can you enlighten me on this topic?
There is a short video regarding SharePoint Tools Project Structure that may be of help to you. The structure of a SharePoint solution within Visual Studio varies on the type of the SharePoint project being developed (sites, content, web parts, workflow, etc). These are folders, namespaces, library & services references, etc. within the VS solution. There are quite a few 'best practices' that can help you - there are two similar questions that were posted in this forum -
I'm uncertain what you mean by "the hierarchy of the visual studio project is unclear"? At any rate...
should get you started on the right track.