Cured resin is a concentrate made from cannabis that has been dried and cured before extraction, the same way flower is prepared for smoking. It is the counterpart to live resin, which is made from fresh-frozen plants.
Drying and curing change the plant's chemistry. Some of the lighter terpenes evaporate, while other aromas develop. The result is a concentrate that often tastes more like a cured jar of flower than a fresh plant. Some people prefer that flavor.
Cured resin can be made with hydrocarbon, CO2 or other extraction methods and comes in the usual textures: shatter, badder, sugar and more. Many concentrates that are not labeled "live" are made from cured material.
Cured resin is often less expensive than live resin, because the starting material is easier to store and handle. It is not necessarily lower in potency, since THC content depends mostly on the plant and process.
If you are comparing products, try a live and a cured version of the same strain if you can, and see which flavor you like better. Check the COA for potency and residual solvent testing, and start with a small amount.