I must say you've pegged the inanometer. Lobbying, at it's most basic, is simply telling a representative your views on an issue. When you or I write to our representative we are lobbying them. Lobbyists are professionals at telling congress what someone wants. They understand the landscape, which politicians would be most interested in hearing about an issue and who not to waste their time with, and are better at it than you or I. Politicians often listen better with campaign donations - a market force at work. If you donate you'll experience this effect as well.