Sitecore 9 form feature is awesome and simple to work with. It is more like Visual Studio Toolbox and you can drag and drop the fields.
I had a requirement from Client asking for Ajax form and wanted to show Confirmation/Success message after the form is submitted. Out of the box, this is achievable with the Form.
Here is a small guide on how to create a form with confirmation message:
1. Select Forms from Dashboard.
2. Click Create button.
3. Select blank form.
4. Drag a page for main content.
5. Drag a another page for confirmation message.
6. Design the fields according to needs. Here I’m doing Email Signup form. You can add field validation and css-class as needed.
Please make sure you have these scripts in Layout.cshtml.