Capacity Planning

Capacity planning is the process of determining the production capacity needed by an organization to meet changing demands for its products. In the context of capacity planning, "capacity" is the maximum amount of work that an organization is capable of completing in a given period of time.

Capacity is defined as the capability of a worker, machine, work center, plan or organization to produce output per period of time. Capacity is a rate of doing work, not the quantity of work done.
(Source : http://www.apicsforum.com/ebook/5b._capacity_management)

Capacity available is the capacity of a system or resource to produce a quantity of output in a given time period.

Load is the amount of released and planned work assigned to a facility for a particular time period. It is the sum of all the required capacities.

Oracle Capacity lets you calculate your capacity load ratio by resource or production line. It ensures that you have sufficient capacity to meet your production requirements.

Oracle Capacity provides you with two levels of capacity planning:
Rough cut capacity planning (RCCP) to validate your master schedules
Detailed capacity requirements planning (CRP) to validate your MRP plans

Capacity Setup

Make sure you set up oracle Inventory, BOM, MRP/ASCP correctly before starting the setups for Oracle Capacity.
The steps shown in the above pic are the set up steps just for the Capacity product. All these setup steps are optional.

Resource Group

Resource groups are used to group key/critical/similar resources.
Resource group is a user level lookup, so you can define as many resource groups as per the business requirement.  Once defined, you can assign selected resources to a resource group in Oracle Bills of Material.

You can choose a specific resource group when using the bill of resources load to generate a bill of resources. You can then use the bill of resources to generate a RCCP plan that only considers the resources contained in your resource group.

You can define a maximum of 250 resource groups, and you cannot change the values in this field after you commit a resource group. To remove an obsolete resource group you can either disable the code, enter an end date, or change the meaning and description to match a replacement code