Orphaned pages are MEpedia entries that have no unique incoming wikilinks from other MEpedia entries. Ideally, all entries would have some inbound links, to best integrate the array of knowledge on MEpedia and help readers access topics related to their interests.
Identifying orphaned pages
You can check to see whether a given entry has any inbound links by looking at the "Tools" column on the left-hand side of the page and selecting "What links here". If a page has no others that link to it, it's an "orphaned page."
You can also see a complete list of all orphaned pages at Special:OrphanedPages.
Warning: Not all entries in Special:OrphanedPages are true orphans. As a technical matter, the software will still list a page as having no incoming links even if it is linked from a category, or from an entry that displays all the page titles in a given category (i.e. has transcluded the contents of the category). Only an individually placed inbound link will remove the target page from the orphaned list.
How to help
You can help integrate an orphaned entry into the project by adding links from other pages that mention the term. You can find these using the search bar: type in the full name of the orphaned entry, but instead of selecting the entry from the dropdown menu, select the option just below that begins "containing..." This will bring you to a full list of all the entries on MEpedia that mention the term. (If entry's name contains common terms, you may need to re-search putting the term inside quotation marks to search for that exact phrase.) Then edit one or more of these pages, adding a link to the orphaned page (subject to MEpedia guidance on using wikilinks).
Once an entry is linked on another MEpedia page, it will automatically be removed from the Special:OrphanedPages list. Assistance working through the list is greatly appreciated! Ideally, the only pages left on that list would be disambiguation pages (since all internal links should preferably point to the specific, intended target page, rather than leave the reader to guess which page was intended.)