We charge based on email providers added. So what are email provides and what are team members and how do these limits differ?

Email providers: 
These are email addresses or alias email addresses that you add to your account for warm-up and/or campaign sending. These are the emails you use to send your campaigns. These are the email slots you purchase for $29/$39/per month per email. 

If you have an account with 10 email slots that means you have a 10x account. These email slots you can add or remove emails from at any time. You pay for the slot, not the exact email so they're swappable,

Team members 
These are members who have access to your account, campaigns, billing, and other users. We do not charge for the addition of team members. You can add as many as you like. These users do not take up your email slot quota.