[Haskell-cafe] Recursion in Haskell

[P. R. Stanley]

Hi
I understand the basic principle of recursion but have difficulty 
with the following:
-- a recursive function
-- for calculating the length of lists
myLen [] = 0
myLen (x:xs) = 1 + myLen xs
What's happening here?
Top marks for a comprehensive jargon-free explanation.
Thanks in advance
Paul