These are mailing lists of a group of people within the same subject interest.
Any message sent to the list goes to the whole group.
They are a useful mechanism for communicating with others interested in a particular subject area. Once you join a list, material is sent to you in the form of messages to your electronic mail box. The groups can vary in their productivity from five to seven messages per day to two per week. If you join and decide a group is not appropriate, it is simple to unsubscribe. Do not add any other words as subscription requests are read by a computer and not a person.