The search function on the Catalog page searches for keywords in the video or collection Title, Full Description, and Tags. Results will only be returned if the searched word is included in one of these three fields.
When creating or editing video or collection settings, ensure the desired keywords are included in the Title or Description, which are located in Details under Video.
Add relevant and easy Tags so your customers can find the content they are looking for. Tags are found under the SEO tab, which is under Content.
Your customers can also search by the custom filters you've added. You'll find Category and Author as two of the default filters, but as you create any custom filters, they will be available for your end-users too.
Just note that filters are single select, so when you click the Category filter, you can only select one category at a time to filter by. Once your customers have filtered, they would need to remove any applied filters (or simply reload the Catalog page) to go back to the non-filtered view.