Mastering form extension is very important because when you are writing modern web services, almost always you will be using form extension to take input from users.  You will be using form extensions frequently for ever, so better master this first.

You can refer to full class documentation here.

The basic form is like this

which generate html code like below

We usually have two types of forms, one that link to the model and one that is not link to the model.

We will look more into how you can build model that work well with forms later.