Definition of a Link Farm

Thread Title:
LInk Farming 101
Thread Description:

I think the views in the above linked thread are a little simplistic, link farming is far more sophisticated than that. C blocks, domains, scripts and network server layouts are all factors in a modern, sophisticated link farm.

The adult guys would know far more about this stuff than I but would anyone at Threadwatch care to expand upon the above in defining a link farm?

See also: this thread at SG Define me a link farm