SOR, i.e., Schedule of Rates, also known as DSR, i.e., District Schedule of Rates. It is a document released by Public Works Departments for every district. It consists of many tables for different activities in construction, such as Concreting, Earthwork, Steelwork, etc. and there different methods and the resources used for that activity and its cost. You will also get an overall price for the activity per unit. The schedule of rates also includes different types of machinery and equipments used and its cost if it is being used in that district.
Note: SOR is not mandatory. It is just to explain the basic rates. The market rate can be a little different from them for any resource.
The following is a screenshot from SOR Delhi for concreting activity with 1:1.5:3 below the plinth level. For a clear understanding.
You can very easily download SOR for any district from the internet.