How do I pass hidden information about a form?

```
<form action="index.php" method="post">
    <textarea rows="2" cols="30"  NAME="com" >
    </textarea>
    <input type="submit" name="com_submit" value="com" />
</form>

```

I need see that the comment is passed for which type of post so I need to pass the value of variable $type also by this form so how should I do that?

I am a beginner so i am sorry if i am asking any stupid question?