I'm not sure if any explanation I'd give you would do it justice...
It's classical instrumental, with some choral pieces here and there, but with some rock influences as well. But that just doesn't really describe it how I want to. It's wonderful. It takes you places, far off places, older places. It's good music to get lost in when you're doing a task that you don't generally find that mentally stimulating.
A lot of the music is used in trailers for films.
This one was used for some Sherlock Holmes stuff for instance: