Its more than just that, its useless. ie:
I will PwNz0rZ j00. U Will C my 1337ness. I r0x0rZ j00r b0x0rZ.
And so on and so forth. Translation:
I will own you. You will see my (e)leetness. I rock(zors) your boxors.
It's not hard to understand. In fact, there is a history behind it...