Visitors who asked to hear from you.
Everybody here did two things: ticked a box on the tour, and then pressed the button in the email that followed. That second step is what makes this a list you can safely mail.
It exists so you can tell the people who walked your tour about the next event, sale or art walk.
You do not have to manage any of this. The states manage themselves and the export can only contain people who are genuinely on the list.
A spreadsheet you bring into whatever email tool you already use: Mailchimp, Constant Contact, anything that takes a CSV.
Export again before every mailing. That is the one habit that matters here, because it is what keeps anybody who stopped out of your next send.
Deletes them outright rather than marking them stopped. Use it when somebody asks to be deleted, which is a different request from asking to be unsubscribed and should be answered differently.
Every sign-up box and every confirmation email links to that page, so nobody is on this list without having been told what they joined.
Read it once yourself, so you know what you have promised on their behalf.