Carmina Burana is a modern, 20th century work but is simple in harmony, unlike a lot of music composed this century. The driving rhythm and fundamental musical instincts allow listeners to respond immediately. In some ways, the work is barbaric and pagan and very potent.
It is a great introduction to serious music, particularly to people who think serious or "classical" music is boring and monotonous.
Classical music refers to music from the period 1780-1820 but the term "classical" is usually applied by the public to Baroque, Classical, Romantic and serious 20th century Music.