Do I have to resell if I get a reseller account?

No, you do not have to resell hosting to anyone else.  The reseller package is called that because it is typically used by resellers, however, it is also useful for customers who have a lot of websites and wish to have separate cPanels for each website or group of websites.  You also get some advanced functionality in WHM, which comes with the reseller package.

Another benefit of getting the reseller package is the fact that it comes with WHMCS.  While WHMCS was originally designed for running a web hosting business, it also can be adapted to be used as a general billing and support system for any type of business you want to run online.