checkbox and radio specify selectable options:
<INPUT TYPE=checkbox> <INPUT TYPE=radio>
reset and submit make the INPUT field a button to clear the form or send its contents to the gateway:
<INPUT TYPE=reset> <INPUT TYPE=submit>
HIDDEN is used to conceal a field that has a preset value that will never change but is unknown to the gateway.
TEXT specifies that a data input field be displayed:
IMAGE displays an image and when the user selects a spot, the coordinates are passed to the gateway.
INPUT is an empty tag, like IMG, with no end tag.