Ok, thanks.

Anonymous wrote:

One more thing... what is the file group actually? Is it a group of users that have access to the file?

On unix you can set permissions to file for its user, for one group of users and for all others. So group of file can be even used to deny access to the file to one particular group, but generaly it is used to grant the access.

If it is, how can I make it so that the file can be modified through a web page?

It depends on your server configuration. Mostly the permissions for "all others" applies to web server. Set the permissions to "rw-rw-rw", while "rw----rw-" may be sufficient.

One more thing... what is the file group actually? Is it a group of users that have access to the file? If it is, how can I make it so that the file can be modified through a web page?

I just meant I want to put contents to a text file/change a jpg file through php, but I can't 'cause I get some error about permissions.

I'm not sure if I understand you. Do you want to change group of file to "www-data"? Use command File > Properties. Note that this may not work for all protocols.

I want to add "www-data" to a group of a file, so I can update the file through browser. How's this done?