What is "Visual C++ express edition?

I should think that if you needed to ask that question, you have absolutely no use for Visual C++ Express Edition. Why did you download it?

I thought that I needed it to run some other programme, but I don't think I do.

I may not need it, but it was free, so I might as well find out what it does.

It is a programmer's tool. Microsoft Visual Studio Express is a set of freeware integrated development environments developed by Microsoft that are lightweight versions of the Microsoft Visual Studio 2008 (codenamed Orcas) product line. The idea of express editions, according to Microsoft, is to provide a streamlined, easy-to-use and easy-to-learn IDEs for less serious users, such as hobbyists and students.

One of these is for Visual C++. It allows you to write and develop programs for Windows.