Web - Companies selling dedicated servers will probably use this for their clients (web servers, duh). Active Directory not included.
Enterprise - Big companies that want to use active directory features will use this edition
Standard - Medium sized companies will use this for active directory features. I don't think terminal services is in this edition.
Small Business - This is for tiny companies (there are something like 10 - 20 CAL allowed (you can't modify them, I think they come with the server)
Datacenter - MASSIVE companies (like MS) use this for mass active directory
I think it's just the amount of memory and CPUs it can support I'm running 2003 std on here and it doesn't seem much different from when I used to run enterprise on my server
Comments
Enterprise - Big companies that want to use active directory features will use this edition
Standard - Medium sized companies will use this for active directory features. I don't think terminal services is in this edition.
Small Business - This is for tiny companies (there are something like 10 - 20 CAL allowed (you can't modify them, I think they come with the server)
Datacenter - MASSIVE companies (like MS) use this for mass active directory