Resources, conversely, are less tangible. Conservative bankers will loan money on reserves. Conservative bankers will not loan money on resources. An example of a resource that will never become a reserve is gold dissolved in seawater. Use of either term by any group depends greatly on whose money is involved, e.g., resources mean your money-reserves mean my money.
Differences can be enormous.
The public, using its money to buy gasoline, is interested in producible reserves, not in theoretical resources. It is known oil that matters for production planning - not oil yet to be found. Published geological and political estimates of undiscovered oil resources have no set time limits stated or implied for the postulated discoveries. Such open-ended estimates effectively imply that the volume of resources yet to be discovered will lie somewhere between zero and infinity and will be found sometime between now and eternity. Such resource appraisals are only considered scientific opinions - regardless of the competence of the scientific or economic committees that originated them, or the elegance of the mathematical assumptions or computer programs involved.