When looking into relationships between websites, there are three types of links.
One-way incoming links
Also known as ‘inbound link’ are links leading in to your site from other sites. Incoming links are the best types of link to get, from a marketing point of view, since they’re offering you something for nothing in the form of free traffic and a boost in the search engines! Sites with a large number of relevant, on-topic incoming links are sometimes referred to as hub sites.
One-way outgoing links
Also known as ‘outbound links’ are links on your own site which connect to other sites i.e. links that will lead your visitors away from your own site. From a marketing perspective, outgoing links may be considered the weakest type of link as you are effectively giving away your traffic. On the other hand, if your site is very useful, your visitors may well come back again – and they will appreciate your site even more for its willingness to point them to other relevant resources. Sites with a lot of on-topic outgoing links are sometimes referred to as authority sites.
Two-way reciprocal links
These are circular link relationships, i.e. your site links out to a 3rd party site, and that site links back to yours. The links might be homepage to homepage, linkpage to homepage or linkpage to linkpage, depending on the arrangement, but they’re essentially a link swap. Reciprocal links can be beneficial when you’re trying to market your site, especially if they are set up between complementary sites, but their value is dropping as the search engines tend to discount such “mutual admiration” relationships.