Stock: Materials, which have the potential to satisfy human beings but human do not have the appropriate technology to access these, are termed as stock. We do not have the required technical 'know-how' to use them for a specific purpose. e.g., water which is a compound of two inflammable gases-hydrogen and oxygen and can be a rich source of energy. We do not know how to use them.
Reserves: These are subset of the stock. They can be put into use with existing know-how but their use has not been started. For e.g., river water is used as a source of hydroelectricity but to a limited extent. Thus, the water in the dams, forests, etc., are reserves which can be used in the future.
