Craft search only shows results matching 'title' of entries
Search via search() can be used only for text fields, if you want to search by categories or records you need to use the relatedTo() method, also do not forget to specify search keywords when creating the field.

Links: https://craftcms.com/docs/3.x/relations.html#terminology, https://craftcms.com/docs/3.x/searching.html#supported-syntaxes.
Practical example:
{% set searchResults = [] %}
  
{% set queryParamsText = queryParamsText|merge({
        search: {
            query: 'title:' ~ searchWord
        }
     }) 
%}

    {% set category = craft.categories.group('category').search(searchWord).one() %}

    {% set relatedParams = relatedParams|merge([{ targetElement:category }]) %}

    {% if relatedParams|length &gt; 1 %}
        {% set queryParamsRelated = queryParamsRelated|merge({'relatedTo':relatedParams}) %}
    {% endif %}

{% set searchResultsText = craft.entries(queryParamsText).section('canAddSectionHandleOrId') %}

{% set searchResultsRelated = craft.entries(queryParamsRelated
).section('canAddSectionHandleOrId') %}

{% set searchResults = searchResultsText|merge(searchResultsRelated)|unique %}