It works on the defined default search field for each collection. The field will be searched with the mysql full text search.
It combines the mysql full text search with some added functionality as described in the advanced search view.
The search is a mysql full text search. This has some limitations. Noticable will be the stopwords. Like searching for "what" will return nothing. https://dev.mysql.com/doc/refman/8.0/en/fulltext-search.html https://dev.mysql.com/doc/refman/8.0/en/fulltext-stopwords.html https://dev.mysql.com/doc/refman/8.0/en/fulltext-restrictions.html