Using a mail address as a group of mail list, are there any solution?

I am not sure whether you encounter this kind of mail address before.
That is when i first create a mail address (eg. list@mailgroup.com )from mail list system. Then once i have to send to the list of receiver,
all i have to do is using a third party account (eg. myMail@gmail.com) to send to that mailgroup address.

Few questions:

1. What is the implementation concept behind?
2. Can it be done on some php code ?
3. What i have to aware of ? (eg. Restrict the third party account so that not anyone access to the mailgroup mail can send to the list)

Thanks for kindly help