Mailing lists let every member of a group send email to everyone else in the group, right from their email account. It's a great way to discuss where to meet, what to talk about and who' s bringing what, without having to keep checking the Meetup website.
Not at all: By choosing this option, you will only receive messages that are sent to the group by the organizers or assistant organizers.
In one daily email : This option is like a daily newsletter. You will receive all messages to the mailing list, but combined into one daily email.
As they are sent: This option works like regular email. You will receive all mailing list messages as soon as they are sent.