I find it very interesting that you would not call an ale a beer!   To me that is like someone saying that Pinot Noir is not a wine!

For beer, the basic difference is the type of yeast that is used and the temperature it is brewed. Of course the taste will be different, but there is no other difference in the product. Except for varieties, you are not adding anything different to a lager or an ale. (Yes, you can add things to either.)

Lagers actually require more care and time to produce, which may be a reason why ale became so popular. Lagers are also less forgiving of mistakes in the brewing process and do not mask the problems as many ales do.