(Not to be confused with terms which is a related concept.)
Keywords is a concept used in connection with Keyword & Term extraction.
Keywords are words (single-token items), that appear more frequently in the focus corpus than in the reference corpus. They can be used to identify what is specific to one corpus (focus corpus) or its subcorpus in comparison with another corpus (reference corpus) or its subcorpus. Comparisons can be also be made between two subcorpora of the same corpus or between the whole corpus and one of its subcorpora.
Keywords can be extracted using the Keywords & Terms tool in Sketch Engine. Typically, the largest corpus in the language will be selected as the reference corpus. The user can set a different corpus or subcorpus as the reference corpus/subcorpus.