Well, after reading the existing answers, I can see that lobbyists are not held in high esteem.
Every group has a lobbyist. Big oil companies have lobbyists, teacher federations have lobbyists, newspapers have lobbyists, doctors have lobbyists and so on.
There are good lobbyists and some that are not so good. I do not want to write a Hub tonight, but I may tomorrow.
Good lobbyists provide information to lawmakers about the issues that concern their clients and to try to urge the lawmakers to vote in that direction. Some lobbyists do make campaign contributions and some do take lawmakers out to dinner or lunch. Some lawmakers will not accept meals from lobbyists.
There are some bad lobbyists. They are bad for different reasons. Just in case you are wondering, President Garfield use to take walks and would often end up at the Willard Hotel (now owned by the Intercontinental Hotel Chain) in Washington D.C. People seeking favors would meet him in the lobby and quickly became known as lobbyists.
By the way I was registered as a lobbyist in Louisiana off and on for several years, depending on the changes made in the law. I never spent one cent on a lawmaker. I did brief a few on issues concerning the industry.