What does Link Farm mean?
Getting other websites to create links to your website remains an important part of improving your search engine rankings.
To cash in on this some people set up websites that consisted entirely of links, usually in the guise of a 'directory' where people could buy or swap links.
Search engines regarded these as 'non-genuine' and so changed their algorithms to discount or ignore links from websites that consisted almost entirely of links.
They classed these in a similar way to reciprocal links.
The strongest links you can have to your website remain one-way inbound links.