Generally speaking, a neologism is any word or phrase that has been newly coined. Many neologisms die without acknowledgement (which is partly why Wiktionary does not include protologisms), but some become diffused in certain specializations or areas of the population, and some become very widely known. The way that language is used has changed and continues to change over time, so neologisms are constantly entering the English language. The lexicographers who write standard dictionaries try to determine how all words are used in English by examining a giant corpus of works, including writings under various publishers. As neologisms become more common, they are more likely to enter dictionaries.
Wiktionary, rather than copying from other dictionaries, requires that it be possible for any entry, and ideally for all entries, to be attested, which is the purpose of citations. A request for verification can be made for any as yet uncited definition that is not in clearly widespread use. Terms such as protologisms that do not meet the criteria for inclusion are regularly deleted.
In some cases, a term will be validated on Wiktionary that does not appear in any major English-language dictionary, or in any of the major dictionaries of a foreign language. These newly acknowledged terms are problematic in that they typically have not been in circulation long enough or widely enough for their social status to be determined. In those cases, the entry is tagged as a neologism to provide such warning.
Neologisms should be used with care, as they may not be understood and, even if understood, may be viewed negatively by language conservatives.