whats the difference? im gonna get a pedal for that so i can go from clean to a distortion type of thing, but im not sure what the difference is. what pedals would you recommend for more of a rock(from metal to alternative) type of approach
OD usually is a little distortion with added bass treble middle etc.
Gear so far:
Dean Vendetta XMT
Roland Microcube

Infiltrate the system and rot it from the inside-out.
Overdrive is just a little less distorted than normal distortion. If you're playing grunge, then distortion is the way to go, because you don't need to be able to discern the different notes and chords as clearly. Stuff where the individual sounds are all important is more of a job for Overdrive.
I think its all about the amount of break up. An OD usually doesn't add that much, so is good for vintage type sounds or tweeking and already distorted sound. Distortion tends to offer more break up, so is less useful as a boost, but should let you get high gain sounds from a clean channel. That's my understanding at least.
Obligatory gear list
Ibanez SZ4020 w/BKP Miracle Man set
Cort X-11 w/EMG 85+81
Tanglewood TSB58 HB w/BKP Nailbomb & Cold Sweat
Epiphone SG Prophecy w/Seymour Duncan/Ibz
Indie Swamp 4
Ibanez BTB 775 PB
Engl Screamer 50
OD is generally used to push tubes/valves. You max out the volume on the OD pedal, turn back the gain on the pedal, tweak your amp and it gives preamp tubes enough saturation to produce 'Distortion'.

Distortion pedal skips all that, takes the direct route of making your signal distorted before entering the amp. You set your amp to a clean tone, the pedals do all the work.

If you have a tube amp, OD is the way to go.
If you have a solid state amp, distortion is the way to go, if you want full on metal/clean tones ofcourse.
cool thnx, then it looks like i need distortion rather than overdrive.
Yeah ofcourse. You can get all sorts of less gain sounds, but generally, you can't really get a modern metal tone from a tubescreamer and an SS amp is all I'm saying. TS only really wants to kick a button and get distortion.
Distortion happens when something is overdriven.

Be it a Pre-amp tube, power amp tube, speaker, microphone, diode clipping circuit, etc etc.
If video games make you violent, does monopoly make you a millionaire?
Overdrive is basically a mild form of distortion. If you can afford it you might want to give a Blackstar HT-Dual DS-2 a try. It has 2 different channels on it - one giving you proper lead distortion and the other giving you a less distorted sound and thus eliminates the need to have both an overdrive and a distortion pedal when you can just use the one pedal.