Internal links, also called blue links because they show up in blue, are links from one MEpedia page to another. In contrast, links to websites outside MEpedia are called “external links”.
Lead and body of the entry
Typically, names or terms that are relevant to ME might be linked once in the introductory section of an entry (the lead), and then again only the first time each appears in the body of an entry. However this is only a guideline, subject to editor discretion. For instance, if an important topic is mentioned twice in the body of a long entry, it may serve the reader to create an internal link both times.
In footnotes (also called inline references), it is preferable to link to all named authors on scientific papers (even if they are cited multiple times in the same entry), as well as journalists and other authors at your discretion. For more information on this, please see MEpedia:Author links.
If a term doesn't have an MEpedia page yet
If it's relevant to ME, go ahead and link it anyway. It will show up as a red link but also be added to the list of wanted pages. Once the entry for it is created, all red links to it throughout MEpedia will turn blue. See more about this at MEpedia:Red links.