You can build web forms that actually submit data to a server using nothing more than pure HTML. You can do this by specifying an action on your form element.
For example:
<form action="/url-where-you-want-to-submit-form-data"></form>
Nest your text field inside a form element, and add the action="https://freecatphotoapp.com/submit-cat-photo" attribute to the form element.
input element should be nested within a form element action attribute which is set to https://freecatphotoapp.com/submit-cat-photo