meaning of following code

[Usmansid]

hi guyz

i needed some help! i picked this up from a new social script i found which requires some validation for joining a network such as email or work website, etc. i wanted to remove that so i was wondering if following line in network controller meant anything to this reference:

$rules[$networkType . '_network_name'] = 'trim|required|min_length[4]';

if($networkType != 'region')
$rules[$networkType . '_network_email'] = 'trim|required|valid_email';

if($networkType == 'work')
$rules[$networkType . '_network_website'] = 'trim|required|prep_url|valid_url|callback__isValidWeb';


if you guyz could explain this to me it'll be great especially the meaning of this line which i think i understand a bit:

'trim|required|prep_url|valid_url|callback__isValidWeb';

thanks