What is the difference between the House of Commons and the House of Lords?

The major difference between the House of Commons and the
House of Lords (I assume that you are talking about the Parliament of the United
Kingdom) is that the House of Commons is a democratic body whereas the House of Lords is
sort of a holdover from the days when Britain was less
democratic.

The House of Commons is elected by popular vote
of all Britons over the age of 18.  The House of Lords is not elected in any manner
whatsoever.  It is made up of people who are either A) senior bishops of the Church of
England or B) "peers" or nobility who are selected by the
monarch.