Terminology around search tools
Confusion sometimes arises about different categories of search tools. Search tool names can be used loosely, but in context of systematic reviews the distinctions matter.
A database is a collection of records representing publications (often journal articles but they can include material like conference proceedings, patents, book chapters, etc.) normally centred around a broadly conceived subject focus. Each of these subject databases will have each record indexed with controlled vocabulary terms which help searchers find relevant literature. The controlled vocabulary might have a specialise name like MeSH headings, or might be more generically called subject headings, thesaurus terms, or keywords. Note that controlled vocabulary keywords are distinct from the keywords used in a free text search.
Databases are often available on different vendor platforms. For instance, Medline can be accessed on the Ovid or the Web of Science platform. FSTA and CAB Abstracts can both be accessed on EBSCOhost, Web of Science, or Ovid. CAB Abstracts also offers its own platform, CAB Direct. The decision about which platform a database is available on will have been made at an institutional level. Both database and vendor platform will need to be captured to report the systematic review searches. <link to reporting>
Another category of search tool are citation indexes, sometimes called citation databases. Web of Science Core Collection and Scopus both fall in this category. They are both very broad in their subject coverage, so broad that a subject focused controlled vocabulary would not make sense since it could not straddle how different terms take on different meanings in different disciplines. However, superficially, they looks as though they use those terms, as they supplement their records with author supplied keywords and keywords generated from the references for each record.
Another category of search tool is academic search engine, specifically Google Scholar. Google Scholar searches academic literature from around the web, but it is not a database. This video below provides a quick overview of some of fundamental differences between a database and Google Scholar.