ISA/TMG/IAG/UAG what is the difference!

Lot of people are confused about the difference between ISA/TMG/IAG/UAG, so I thought it would be a good idea to share this information hopping it will clear up this confusion.

Microsoft has lately released the “Forefront Threat Management Gateway (TMG)” formerly known by “Internet Security and Acceleration Server (ISA)”.
Microsoft has also released the “Forefront Unified Access Gateway (UAG)” formerly known by “Internet Access Gateway (IAG)”. By the way both products are run on 64bits only

So this means that TMG is the new version of ISA and UAG is the new version of IAG, mmm pretty simple right?

What is the Difference between TMG and UAG?