Seeing as how I'm not allowed to post links here ( <_< ). PM me and I'll give you a link
Basically, it's the newest way of playing Dark Elves. It stands for Multiple Small Units. It was meant as a means to combat swarm armies (and does so very well), but it has also been found that by combining it with MSE (Multiple Small Elites) it can take most armies pretty effectively. It's being used to beat Chaos nowadays.
It's pretty good, although I didn't like it at first glance. It takes advantage of the dark elf army list- fast, high Initiative troops, good WS, tactical spells, and the overall 'elitest' feel of our army.