In order to use autoresponders you need to capture peoples emails with your squeeze page.
Now let's say that you have a small list of subscribers of 1,000 people and you want to send 1,000 emails, autoresponders are awesome because they allow you to email all of them by just writing 1 email, selecting the list that you want to send your email to and clicking send (you can also schedule your emails of sent them in a sequence).
There are two kinds of emails you can send with autoresponders:
1. Broadcast: this option will allow you to send an email to your entire list the moment you write it or schedule it.
With broadcasts you have the ability to target countries, i.e. you want to promote a contest that is only available to the US, thanks to this feature you can target only the US and send your email without worrying people outside the territory getting you promotion, after all they wouldn't be able to enter the contest anyway.
2. Autoresponder: this one is time based or action based, you can program your autoresponder to send an email as soon as someone opts-in your mailing list or program it to send a sequence of let's say 10 emails in 10 different days.
So.. in day 1 they get the first email, day 2 the second, day 3 the third and so on and on.
It looks like this:
If you want to try an autoresponder I highly recommend GetResponse, they give you a 30 day free trial, you don't need a credit card and you can use the full features they have.
They also have the GetResponse Academy where they teach you how to get your fist 1,000 subscribers in 30, 90 days, it's free as well, you can try it.
I hope this information helps you understand a little bit better how autoresponders work and what you can do with them.
Regards,
Jonathan N