Thank you :D
Mabon is the Autumnal Equinox; Litha is the Summer Solstice [longest day] and Yule the Winter Solstice [shortest day]. Beltaine, Imbolc, Samhain and Lammas are the 'cross-quarter' days which are roughly between the other festivals and considered more traditional, marking important farming calendar dates, than the astronomical equinox/solstice dates.
I'm thinking I should put up a post with the Wheel of the Year showing all eight festivals for anyone who is interested; a nice project for between now and Beltaine [Mayday] :D