Difference between Lager and Bitter

[5freemen]

What's the difference between lager and bitter. I've been told that lager is bottom fermented and bitter top fermented, but what does this actually mean. How does this affect the taste?

[Xollob]

Wikipedia gives a good introduction to top and bottom fermenting yeasts. Top-fermenting yeasts, which are used to brew bitter at a higher temperature than bottom-fermented lager, are unable to ferment some types of sugars, and the resulting beer is sweeter and "fruitier".

[tubeway]

Also lager is brewed at lower temperatures than bitter - they both use different hops, the malt is different, they use different adjuncts