Forms are not a service that Prismic provides, but luckily if your website need to use forms it's easy to set different services alongside Prismic in your applications frontend.
You have two options when it comes to using forms with Prismic.
Option 1: Third Party Services
This is by far the easiest way to add forms and usually what we recommend using. Third-party services such as Formstack, Wufoo or TypeForm can handle this very easily. Just sign up, create the form and add the link or script they give you.
Note: Prismic has no affiliation with any of these services. Some have free tiers and others charge, each with their own advantages and disadvantages.
Some of these work natively with Prisimc's Embed field, and for any that don't you can setup a field for custom HTML/embed code as explained in this article:
Option 2: Custom Set-up
You can setup fields in Prismic to define the text that appears on the form (such as the field name, placeholders, and default text). But the form's functionality needs to be handled on your end or by a third party service.
On your front end you will need to set up the form's input fields with the text pulled from Prismic and write the code to determine what happens on submission of the form.
I hope this article helped you better understand the concept of using forms alongside Prismic in your website application.