An explanation borrowed from The Columbia Encyclopedia, 6th ed:-
"Lobbying practice and profession of influencing governmental decisions, carried out by agents who present the concerns of special interests to legislators and administrators. The term originated in the United States of the 1830s, when representatives of interest groups tended to congregate in the lobbies of Congress and state legislatures. It is now used in a broader sense to include attempts to influence any governmental actions". ("lobbying," 2012)
See also V. O. Key, Politics, Parties and Pressure Groups (5th ed. 1964); A. M. Scott et al., Congress and Lobbies (1966); S. Farkas, Urban Lobbying (1971); G. Wooton, Interest Groups (1971); M. T. Hayes, Lobbyists and Legislators (1984); C. Barnes, The Politics of Policy-Making and Pressure Groups (1987); R. G. Kaiser, So Damn Much Money (2009). ("lobbying," 2012)
So in layman terms, if you want to get work done which is of interest to your organization or public at large you will try to locate all possible people in position of authority who are useful to you in influencing other people in position of authority, to get your work done.It could be social issues or environment issues or amending policies which affect public at large or for organisations to start with new projects and business both nationally and internationally.
Anyone can lobby and methods of lobbying vary which includes making presentations, sending letters, briefing people in authority and even organizing rallies to get your voice heard on issues of public interest or the organization's interest. Read on http://www.parliament.uk/get-involved/have-your-say/lobbying/
If anyone can lobby why is this process illegal in many countries? The answer lies in the fact that there is not a legal act in place like in some countries. Here they call it the "Lobbying Disclosure Act" ref.http://lobbyingdisclosure.house.gov/amended_lda_guide.html Here is a checklist of some countries and the act of lobbying http://en.wikipedia.org/wiki/Lobbying
Lobbying is also tricky to regulate says this article on Holmes Report http://www.holmesreport.com/featurestories-info/11835/Analysis-Does-Lobbying-Regulation-Work.aspx Here they have extensivley discussed a guide to lobby legislation by Raj Chari (Trinity College
Dublin), John Hogan (Dublin Institute of Technology) and Gary Murphy (Dublin City University).Check http://www.regulatelobbying.com/index.html
If you read the articles it again brings to our notice that the influence of culture of a country and the practices in turn is shaped by it.It is no doubt that lobbying should be regulated but how and how much is a questions which looms large.
Hope this article sheds some light on the issues related to lobbying. Your views are welcome to further understand this crucial subject.