It simply means that after every post you post to a board, you have to wait 120 seconds before another post will go through. It doesn't sound like a long time until you find yourself sitting there, watching your computer clock, waiting for the time to pass.
The worst thing of all is that if you get impatient and click it too soon, it takes you back for ANOTHER 120 seconds. The more impatient you are, and the more likely you are to click too soon, the longer you're going to be waiting for those posts to go through.
And it doesn't matter if you move from one board to another. It's also the same with PMs......you have to wait out the time or your posts and messages will simply not go through.
I'm the impatient type.....believe me.....I know...
