[TYPO3] what is the fconf and how does it differ from the conf

[dave typo]

I dont understand this line that I came across while looking at
extensions...


// bring in the fconf.
            $this->fconf = $this->cObj->fconf;

//

function validate() {

$this->validated = false;

$extension = strtolower(substr(strrchr($this->attachment['name'], '.'), 1));
                $allowed =
explode(',',strtolower($this->fconf['allowed_file_types']));
                if ($allowed) foreach ($allowed as $key=>$value)
$allowed[$key]=trim($value);
                if (is_array($allowed) && in_array($extension, $allowed)) {
                    $valid_6 = true;
                } else {
                    $this->error['attach_type'] =
tx_chcforum_shared::lang('validate_type');
                }

}
what does the fconf do and how is it used?

how does it differ from the conf?

I'm trying to do something similar in my php coding, as I cannot get my code
to check file extensions....

thank you everyone,

again,

-dave