A customer is anybody who either
i) Buys something from you
ii) Creates an account (whether or not they have bought something from you).
When somebody does one of these 2 actions they'll appear on a page, in your account, labelled 'customers'. On this page you can view information about them.
When you click 'edit' next to a customer, or hover over their name, you can then view more information about them.
You'll be able to view their email and postal address, how many orders they've placed and what they've spent, and whether they're happy to receive marketing communications (like newsletters) from you.
We also have another type of customer account available called 'trade customers'. Trade customers have different features to normal customer accounts in that you can enter special pricing for them and give them credit accounts. Read more about trade customers here.