A mailing list is a group of people who share their ideas with one another through the medium of a EMail list. You use mailing lists through the medium of EMail and each 'issue' of the magazine is really just EMail from some other subscriber. For an example if you had a good peanut butter cookie recipe you could mail the list your recipe and everyone would get a copy. To receive the messages sent to a mailing list you need to join or 'subscribe' to the mailing list. The list address is the EMail address that you use to send messages that you would like to share with the other members of the list.
Mailing lists are fun ways to share ideas and interests with a like-minded group of people.
They are similar to Usenet News Groups except that anyone can read or post to a Usenet group, whereas only members of a list can take part in the discussions on that list. Part of the 'nettiquette' of using mailing lists is to make sure that you only send messages to the lists that concern, or are of interest to, all the members. If you have something that you want to discuss with only one or two members of the group, you should do this via private EMail rather than through the list.