Multiple domain hosting refers to a web hosting arrangement in which the provider allows you to run all of your domains on one single web hosting account. With multiple domain hosting your apportioned server resources (ie. disk space and bandwidth) are divided into parts to accommodate multiple websites. This arrangement allows you to save a lot of money because you only have to pay for a single web hosting plan but host multiple websites.
In additional to cost-saving, multiple domain hosting also gives you the ability to manage all the web hosting features and services for each individual website via a centralized control panel.