Hello, Jessica.
You can override the following language constants under Joomla admin -> Extensions -> Language -> Overrides
MOD_AGS_FILTER_TYPE_TAG
MOD_AGS_FILTER_TYPE_KEYWORD
MOD_AGS_FILTER_TYPE_CATEGORY
You can find other contants in this file - languages/en-GB.mod_articles_good_search.ini
Also, you can find it by text in override form.