Let's start by talking about what a list is. A list is people who have opted to receive emails from you. They may have visited one of your websites, or any Web 2.0 property or something similar that you own, and said, "I want some information," and filled in a form on your page. It may be have been a popup, an unblockable popup. It may have been just a form on the page. Whatever it might be, they've said they want to receive emails from you. Usually, it's related to a website that you've created. So, if you've got a website on stopping smoking, you might have a stop-smoking list. If you've got one on parrot keeping, you might have a parrot-keeping list. If you've got one on cooking, maybe you've got a list on that as well.
But, they've signed up to your list for a reason, because they want more information on the subject that your website's about, the niche that you're marketing in. They either want the free gift that you signed up, or if they're not quite sure to buy your product yet, so they want some more information, or they want the course that you're offering to give them access to, or anything like that. That's why they've opted in. Typically, your list is going to contain people from all over the world. Don't be surprised if there are people who don't come from your country. Don't be surprised if there are people that don't speak the same language as well as you or don't understand the colloquialisms you use or some of the terms you use. There are going to be people that are going to be experts in the niche. There are going to be people that are intermediate, and there are going to be people that are complete beginners and have no knowledge whatsoever. What you may also find, if you start being successful in the niche, you're going to get some of your competitors subscribing to your list as well because they're going to want to check you out and see what you're doing.