Why after importing Standard Assets my Visual Studio Solution has 3 projects ?

Hi!
I’m new with Visual Studio and I’ve been wondering why are there 3 projects inside my solution. They appeared after I imported some Standard Assets to my game.

I’ll add an image so you can understand better what I’m talking about:

So my questions are:

  1. What is each project for? I’d like to understand what are Unity and Visual Studio doing behind the scenes to make this 3 different projects part of the solution.
  2. Can I add more projects to my
    solution to structure the code and
    still make everything work as in one
    single project?
  3. When it could be a
    good idea to divide code in different
    projects inside a solution?

I’ve tried searching online but I could not find anything about how Visual Studio solutions/projects relate here to Unity scripts.

These are the default files that get installed with all the standard assets ticked in unity when creating a project, visual studio is just recognising the namespaces been used is different between them all and has tried to but all the files in the same namespace together. Nothing to worry about its normal.