Reseller and Owner (only if reseller) in WHM? Anyone know the difference?

Make the account a reseller.
Make the reseller own it's own account.

Owner has no effect if reseller is not checked.

 

The "person" you created the account for owns it of course, but if you create the account as root, it means by default, root is the one who controls the account. You make it a reseller and it means that account gets a WHM to create more accounts, but unless you make that reseller own his own account, he has no control over it, only ones he creates.

 

Reseller

Imagine the following:

You create the reseller an account with domain example1.com with 1 GB space and 5 GB monthly transfer.

This reseller has 3 GB space and 20 GB monthly tranfer.

Do you want this account to be included in this reseller's resources?
Do you want the reseller to be able to change this account's quota and data transfer limits?

If you do, you'll have to check the owner. Otherwise, like squirrel wrote: root owns this account. Any modification will have to be done by root and not by the reseller.