Web Form iFrame
The Web Form URL inserts an iFrame containing your web form. Most people start here.
Pros: Easy to use. This is the only code where changes made in the Web Form builder are instantly updated on your page.
Cons: Hard to customize beyond what is in the web form builder. May not fit everywhere.
Use this when: You're first starting out. You don't need to customize your form. You're unfamiliar with HTML.