The word lobby has two main meanings:

1. A lobby is the entrance area or waiting room of a building, especially a large one like a hotel, theater, or office building. When you walk into a movie theater, you pass through the lobby before entering the actual screening rooms. Hotel lobbies often have comfortable chairs, a front desk, and decorations that give visitors their first impression of the place. The lobby is a transitional space: you're inside the building, but you haven't quite reached your final destination yet.
2. To lobby means to try to influence politicians or decision-makers to support a particular cause or pass specific laws. Environmental groups might lobby Congress to protect forests. Business owners might lobby their city council for better roads. Today, professional lobbyists meet with elected officials to present facts, arguments, and perspectives on behalf of organizations or causes. While lobbying is a legal part of democracy, it can become controversial when wealthy groups have more access to politicians than ordinary citizens do.