stereo experts in here

I just sold an old car and have an amp and sub that I kept out of it.It is an Alpine 4/3/2/ channel + subwoofer drive power amplifier(MRV-F352). I was running 2 speakers and a sub in a small cabin with this and it really rocked.
I don't have the owners manual but have one on order. If I remember right it didn't really throw alot of power to the speakers but was pretty good at the sub,(100 watts, I think). What does "bridged" mean. I remember by doing this it really upped the power. How do you do this and is it still stereo when you do? Can I run 4 speakers and a sub with this amp?

After further inspection, channels 1 and 2 are actually marked "bridged" and have their own connections while channels 3 and 4 are regular hookups; channel 5 is a separate output for the subwoofer. So, am I correct in that in order to run 4 speakers and a sub, two of the channels will be bridged and two will not? Why would they make an amp like this and why would one want two channels not in stereo?
I will of course wait for the manual to arrive but wanted to try and learn what I could first. My head unit puts out 40 watts per channel and I don't think the amp puts out much more than that, (except for the bridged channels, which I think double the output), so would it be better to hook everything up to the amp until I can upgrade or just use the amp to power the sub for now?

Thanks for the help. I figured out that I can run 4 channels and a sub. None of them will be bridged. Specs at 14.4 volts are 50 watts rms x 4 at 4 ohms plus 150 watts to the sub, 60 watts x 4 at 2 ohms plus 150 for sub. At 12 volts, those numbers drop to 30 plus 100 and 40 plus 100, so my charging system better be working!