[Boost-users] boost concept creation

Can someone give me a high level explanation of the idea behind how concepts work? I'm trying to write a new concept class which enforces that two types are the same and it's not quite clicking. Strangely gcc has this concept built in, so I was surprised that boost didn't. I noticed a boost::is_same<> template, but it's not a concept, so it's not usable inside a BOOST_CONCEPT_ASSERT() macro.