The difference is that only you subscribe or unsubscribe yourself to the list and you, therefore, choose in which mailing lists you wish to be included. Internet users who are interested in a given topic may subscribe and then read and contribute to the electronic mailing list. These subscriptions are part of your Internet access so there is no specific cost associated with your use of mailing lists. Some lists are moderated which means that a human being scans every submission and decides if it is pertinent to the list. Moderated lists are more likely to have more productive discussions or information which remains focused on the list topic.
Mailing lists can be an unbelievable source of information.
On the other hand, there certainly are lists out there that will not contain very much useful or high quality discussion. Feel free to pop on and off of lists until you find the ones that meet your needs. Also, remember that if you subscribe to mailing lists you are making a commitment to check your mail on a regular basis so that the mail does not build up in your electronic mail box. Locate the list in which you want to participate. Subscribe to the list.