Pardot comes with many features that can help you build a relationship with your prospects, and one of the most beautiful features in Pardot is Completion Actions.

Completion Actions help you to trigger actions on prospects whenever they interact with your marketing assets. For example, whenever the prospect fills out the form on your website you can add them into a list OR send them an autoresponder email.

Completion actions are available for:

Forms
Forms Handler
Custom Redirects
Emails
Page Actions

Considerations for completion actions:

Completion action works only when the prospect has submitted a form on your website, they do not work retroactively.
Completion action works only for Prospects not on visitors.

Note: Completion Action works only when the website is connected to Pardot, and you are using the Pardot form or Form Handler on your websites.

Autoresponder Email with Completion Actions

Autoresponder Emails are emails that are triggered automatically whenever the prospect engages with your marketing assets.

Autoresponder emails can be used:

After prospects submit a form on your website, prospects receive an autoresponder Welcome Email.
prospect submits a form to download a file on your website, receives an autoresponder email with a link for downloading the file.
A confirmation email for event registration.
and last but not the least, a simple follow up email.

You can set and trigger as many actions you want in one Completion Action.

Here you can check this Screen Prompt of Completion action.