For now, there is no commerical aspect for customers area as you might think.
The customers area is more like a way for you to keep things separate if you handle the email marketing for multiple websites.
After you install and setup MailWizz EMA, next step is to add a new customer in order to be able to create email lists, campaigns, etc.

Company info One important aspect for customers is the company info, each customer must add the company info in order for MailWizz EMA to build the email footers later when a campaign is sent.
Please note, you are required to have the company info footer, otherwise you will not be able to send campaigns.
Also, when you create a new email list the company info will be inherited in the list details, so having it set in the customer account will make things easier for you.

Another important thing regarding customers is that you can impersonate them, that is, login as one particular customer from your backend panel and have full control over that account(this includes lists, subscribers, campaigns, api keys, etc).