Forms are HTML base objects, enclosed by <form> and </form> tags.
<input name='xxx'>: Text input fields
<form action='xxx': URL to send the Form to. If empty send to the current URL.
Exemple:

<form action="/action_page.php"> 
  First name: <input type="text" name="firstname" value="Mickey">
  Last name:  <input type="text" name="lastname" value="Mouse">
  <input type="submit" value="Submit"> 
</form> 

Post a Form thanks curl:

$ curl -X POST -F 'firstname=Mickey' -F 'lastname=Mouse'  http://12.10.1.11/action_page.php