Can anyone describe what the off flavors such as tannin taste like?

I've read many times that if your temps are too high (I think) that you can get off flavors such as tannin in your beer. I'm just wondering if anyone could describe what that would taste like? Is it a different kind of bitter on your tongue after you swallow? Is it a metallic taste? Just curious. I've made some beers in the past that had some "different" tastes to them and am trying to figure out what they're from. I'm pretty good about the sanitation side of things so I don't think it's coming from that. I guess I also don't really know what a "yeasty" flavor is either. If anyone can shed a little light on this for me I'd appreciate it. Thanks.

Best way I could describe tannins really doesn't involve flavor.  The way I pick them up is best described as more of a clenching in back of my mouth as it passes of this part of my tongue.  Find a good Cabernet or Zinfandel and you should be able to experience it.