Potential resources are the resources which are currently not fully utilised. We do have the technology to extract them but their extraction has not been started yet at a larger level. Reasons can be lack of investment, for e.g., Rajasthan and Gujarat receive plenty of solar energy and have plenty of wind energy, but the use of these resources so far has not been developed properly.
Developed resources are the resources of which the quality as well as the quantity has been surveyed and utilisation has been determined. On the other hand, the development is said to be based on technology as well as their feasibility.
Stock is the resources for which presently, we don’t have any technology to extract them. For e.g Water consists of Hydrogen and Oxygen. Hydrogen is considered as one of the sources of energy but we do not know the technology to extract energy from it.
Reserve resources are those which we are not extracting them at present in spite of technological availability. They are stored to meet the world's future requirements.