You're right - I also found the symbols unintuitive, confusing to say the least when I installed mine.
L is Live
X (crossed out wavy line - good description!) connects to the load (bulb). The other end of the load goes to Neutral
S is only needed if you have 2 (or more) switches controlling the same light. In this situation, you just link all the S terminals together. You'll need 1 master switch, then the others are (cheaper) slave units.
I've been well impressed with my light switches & plug-in dimmers so far - apart from an early failure which they replaced immediately.