After a visitor completes a form on your website, you'll want to send them to a landing page letting them know that their form has been submitted. This page is the perfect place to say thank you, and to ask them to download a document, visit another page on your site, or take any other action that would be useful for them.
And this Thank You page is trackable in Google Analytics when you set up a tracking goal. The data you capture through this goal will be a piece of your analytics puzzle, and will help you determine if your site is performing as you expect.
About Goals in Google Analytics
Goals measure how often a visitor to your website completes a specific action. In the case of tracking a Thank You landing page, Google will track how many visitors arrive at that page by completing your form. This type information is essential when measuring whether your site is meeting your target objectives.