You can read whatever you receive, but you do not have the opportunity to discuss it with other subscribers. Each list has its own purpose, scope and membership. Large lists have more than 10,000 subscribers, and small ones have less than 100. Some lists are very strict with rules, and some are very informal and you find many personal messages. Some lists approve subscribers individually, but most of them automatically accept subscriptions, though some of them ask for confirmation or a questionnaire about the subscriber.
Some lists have passwords for special operations.
In order to post your message to a list, you have to subscribe to it. A very few lists require special authorization to post messages. Some lists are moderated, and contributions are screened before they are posted. Others are unmoderated, and all contributions are distributed to all subscribers automatically. On a list, you can get information on your field.