Hi Jaisree,
I'm not sure whether you are asking about how/where the availability of your capacity should be defined, or actually you want to know what are the components/factors that determine the free available capacity.
I went ahead and looked over explanations for the measure factors you spoke about...
The availability of a capacity is calculated taking into account values such as operating time (including break times) and number of individual capacities.
Please check the following links, you will find specific content regarding capacity planning:
Brief explanation about capacity planning
Thread discussion, here you will find a explanation regarding Order and Resource Reporting
Articles about Available Capacity and it's calculation formulas:
http://help.sap.com/saphelp_erp60_sp/helpdata/en/d2/febb37f8f82c76e10000009b38f8cf/content.htm
http://help.sap.com/saphelp_nw70/helpdata/en/c1/ac865342bc3d58e10000000a174cb4/content.htm
I hope it might be helpful.
Thanks,
Pablo