What is the difference between Visual Studio 2008 Standard and Visual Studio 2008 Professional?

Microsoft has provided multiple answers to this question:

(1)  This answer is quick and high level:

http://msdn.microsoft.com/en-gb/vs2008/products/bb980920.aspx

(2) This answer is less quick and slightly more detailed:

http://msdn.microsoft.com/en-us/library/zcbsd3cz(VS.80).aspx

(3) This answer is very detailed.  It comes in two flavors:

Web: http://msdn.microsoft.com/en-us/vs2008/products/cc149003.aspx

Downloadable: http://www.microsoft.com/downloads/details.aspx?FamilyID=727bcfb0-b575-47ab-9fd8-4ee067bb3a37&DisplayLang=en