Ah, OK. So, a "solution" is made up of many projects, which is made up of many files? It sounds very enterprise-y. I'll promise to stay out its way, as long as it stays out of mine.
And I guess I can get by without knowledge of what a Team Foundation Server is or does.
All of these together form a 'solution'. So, in that sense, the term 'Solution Explorer' kinda makes sense if you squint right. Whether or not the word 'solution' is appropriate at all is a different issue entirely...