You're seeing just the function unaccented_search_params, go back to Forage.SearchPostgreSQL module for more information.
Link to this function

unaccented_search_params(params, field)

Convert a search term into params that can be used in a forage plan. Search will be case-insensitive and will ignore accents.

Currently this function requires PostgreSQL.

This is implemented internally as an ILIKE operator. Thus function calls the special forage_unaccent() function, which you should have defined somehwere in your PostgreSQL database.

If it makes sense for your application, you can implement better search yourself.