A plan is a set of hosting resources. Sometimes a plan is also referred to as a hosting package. Creating and offering different hosting plans/packages is a common industry standard in the web hosting world. If you want to initiate your hosting business then you should know how to offer vaious services and resources to the users.
Basically a plan is a set of different resources and services you are offering to your customers. You can offer various types of plans to users depending on the their requirements. Once a plan is sold and your customer request for some additional resource or service then it can be perfectly handled by Add-Ons feature available in this section. For Example: you sell a plan with a limit of 1 GB disk space. If later on, the user demands for 1 GB more disk space under the same plan then it can be sold via Add-Ons.
Also there are different properties of various resources such as mailbox is a resource and its size is one of its properties. So, you can easily manage users' resources and its properties through HC panel under this section. You can set different properties for different users as well.
