Mailing lists are e-mail based discussion groups.
If you're a member of one, you can send a message to the list address, and it's then sent to all the other members on the list. Other members can reply directly to you or, if it's of general interest, to the whole list. This is a relatively young and quiet e-mail list for UK topics and people and those interested in them. This is the oldest and most international e-mail list for DS, and probably has the most subscribers. It's therefore quite busy.