The most efficient way to use this SEO Glossary is to read the concise definition, and if the definition is hyperlinked (underlined), then you can click that term to go to a more in depth article explaining that particular term or concept.
Back in the olden days, search engines used to simply display the top 10 links that were presumed to be the best matches for a search query. Google, obviously the dominant search engine, used to use this display format as a way to signal 'outdated' content.
As Yahoo, Bing, and other search engines were/are always competing for the remaining market share in search, Google kept/keeps innovating at light speed. One way of doing so was adding content previews, displaying more results, and paginating without an unwavering set number of 10 links per page. Though 10 links per page is still the standard, there are now sponsored listings and news articles that are differentiated by their displays. Try Googling, "Rice Cooker" to see what I mean here. Now, we simply call these SERP's (Search Engine Results Pages), the definition of which we'll have a linked article, and a concise definition on this page, in no time :)
A backlink is a hyperlink from another [usually related] source page pointing to a page on your site. Backlinks can be internal links within your own site that point to another section of the current page or a related page on your site. They can also be from external source pages, referencing your site. Both of these kinds of backlinks are On-Page SEO and Off-Page SEO, respectively.