I believe that beer is a general term used for lager, as in "Do you fancy a beer", where mostly it infers a pint / drink of any kind, namely lager, although a lager is not a beer.
I think that beer is actually ale; real ales being the malty flat ones like Morlands Original, Speckled Hen, Bishops Finger, IPA etc that are stored in a keg at room temp, and lagers being the fizzy ones like Stella, Fosters, Kronenbourg, etc.
according to my little book.proper Beer is top fermenting,while lager is bottom fermenting, which produces a more gaseous brew. Beer is usually tastier,rounder,fruitier and more complex while bottom fermenting lagers are refreshing,crispier and cleaner.I find lagers all "taste" the same