Two-way linking, reciprocal linking or return linking. You exchange links. This is a very common phenomenon and is often a win-win situation where you market each other. When it comes to linking I recon that an ordinary web site got 80 percent Two-way linkings of all incoming links. The rest, 20 percent are One-way links (also called inbound links). One-way links involves only one link; one link to your web site from another web site and no return link. One-way links are viewed to carry a higher weight and importance for the search engines (E.g. Google is giving you a higher ranking and a better listing in their index). Why? Getting One-way links are (more) difficult, or more expensive. If you want people to link to you without you linking to them, you have to offer something of value that people will post on their web sites. This can be great content, tools, informative articles, an affiliate program and so on.

Another form of linking is Three-way links. I say it's fraudulent. Why? It is hurting search engines Page Ranking system. Three-way links looks like One-way links, but it is actually a "well planned" (and stupid) trade of links. One webmaster is mastering two web sites and is giving a One-way link to a second webmaster's web site which contains a One-way link to the first webmaster's second web site. These web sites are not having great content, tools, informative articles, an affiliate program or what so ever. They are cheating the system and their web sites are believed to be banned and removed from search engines index when detected. Stay away!