The password fields are a special category of the input tag. Still, writing them is as simple as writing a normal text field.
<input type="password" size="5" maxlength="5" /> <input type="password" size="10" maxlength="10" />
And the result, is a field in which the text is hidden under asterisks, stars squares or black circles, this depending on the browser's interpretation.
As you can see, there is no big difference between the structure of a normal text layer and the structure of a field that contains a password.
It must be mentioned that these password fields are not encrypted, and using them without any safety measures as it was presented above is not recommended.
Sending encrypted passwords to the server can be done using SSL/HTTPS. Another way would be to use .htaccess (if you're using Apache). But this are tecnical stuff that you will learn at a later time.