Reciprocal link
A reciprocal link is a mutual link between two objects, commonly between two websites to ensure mutual traffic. Website owners often submit their sites to reciprocal link exchange directories, in order to achieve higher rankings in the search engines. Reciprocal linking between websites is an important part of the search engine optimization process because Google uses link popularity algorithms (defined as the number of links that lead to a particular page and the anchor text of the link) to rank websites for relevancy.
Resource Linking
Resource Links are a category of links, which can be either one-way or two-way, usually referenced as "Resources" or "Information" in navbars, but sometimes, especially in the early, less compartmentalized years of the Web, simply called "links". Basically, they are hyperlinks to a website or a specific webpage containing content believed to be beneficial, useful and relevant to visitors of the site establishing the link.
In recent years, resource links have grown in importance because most major search engines have made it plain that - in Google's words - "quantity, quality, and relevance of links count towards your rating."
The engines' insistence on resource links being relevant and beneficial developed because many artificial link building methods were employed solely to "spam" search-engines, i.e. to "fool" the engines' algorithms into awarding the sites employing these unethical devices undeservedly high page ranks and/or return positions.
Despite cautioning site developers (again quoting from Google) to avoid "'free-for-all' links, link popularity schemes, or submitting your site to thousands of search engines (because) these are typically useless exercises that don't affect your ranking in the results of the major search engines - at least, not in a way you would likely consider to be positive," most major engines have deployed technology designed to "red flag" and potentially penalize sites employing such practices.