Content is the name given to a 'yes' vote in divisions in the House of Lords and indicates a vote in agreement with the proposal being discussed. The Not Contents are those who have voted 'no' to the proposal. Members of the House of Lords show that they agree with a proposal by going into the Contents Lobby during a division and use the Not Contents Lobby to vote against a motion in the divisions. In the House of Commons they have Aye and No Lobbies.
Further information on this subject can be found from the following links.
House of Lords Hansard
Related glossary term: Aye and No Lobbies