A special-interest group has hired George Pappas to speak to Congress members about H1-B visa legislation. The corporation wants to relax restrictions on who can receive these visas and wants to influence legislation in its favor. George is an example of

A lobbyst is a person, who can be hired by a corporation, or can work independently, and seeks to persuade members of congress to enact legislation that benefits him or the corporation he works for in a particular way.

Lobbysts are controversial because the pursue a wide variety of interests, and not everyone agree with the things they lobby for. For example, lobbysts that work for logging companies are obviously seen as controversial by many enviromentalists. However, being a lobbyst is not illegal as long as the lobbyst does not commit acts of corruption (for example, offering money to a member of congress in exchange for favorable legislation).

In this example, George Pappas is a lobbyst. He has been hired by a corporation to defend H1-B visas in front of congress, probably because said visas benefit the corporation in some way, most likely, in the form of lower wages, or high human capital.