I'm confused about what reseller hosting actually is. Is it for you personally to resell to others or is it used so that you can host more than 1 domain at a time (or both)? Any answers would be appreciated. Thanks.
Yes you can, at some companies you will get the chance to add unlimited domains. If you take a reseller with CPAnel you will most likely get WHM. That way you can add packages, users, set limits etc
Reseller hosting plans are often divided into several plans to be resold to others. If you had a reseller plan, you could offer others with hosting services. Sometimes web developers will buy a reseller hosting plan to use to host their various sites.