Classification of resources on the basis of development is as follows: 1. Potential Resources: Resources which are found in a region, but have not been utilised are called potential resources. For example, the western parts of India particularly Rajasthan and Gujarat have enormous potential for the development of wind and solar energy, but so far these have not been developed properly. 2. Stock: Materials in the environment which have the potential to satisfy human needs but human beings do not have appropriate technology to access these, are included among stock. For example, water is a compound of two inflammable gases; hydrogen and oxygen, which can be used as rich source of energy. But we do not have the required technical know-how to use them for this purpose. Hence, it can be considered as stock. 3. Developed Resources: Resources which are surveyed and their quality and quantity have been determined for ulilisation are called developed resources. The development of resources depends on technology and level of their feasibility. 4. Reserve: They can be put into use with the help of existing technical ‘know-how’ but their use has not been started. These can be used for meeting future requirements. For example, river water can be used for generating hydroelectric power but presently, it is being utilised only to a limited extent. Thus, the water in the dams, forests, etc. is a reserve which can be used in the future.