label: IDE, book
I agree the project is a more important development concept, but the solution also has unique, important functionalities. I found many of these functionalities from [[MSVS 2010 unleashed]].
* project dependency is described in the sln file.
* you can build an entire solution, according to the predefined build order
* a solution can contain so-called non-project items such as documentation. All such files are by default put into the “Solution Items” virtual folder.