Some beans are better used at the dried stage than at the “green bean” stage, because their pods are so fibrous.
Others can be used at the “green bean” stage, though they may not be stringless.
Dried Beans can come from pole or bush bean type plants.
Home gardeners don’t usually grown beans for drying, because there’s no taste difference between home dried beans and dried beans bought at the store (though home gardeners might grow obscure varieties not available in stores.)
Beans purpose-grown to become dried beans include Black (aka Turtle) Beans, Kidney Beans, Navy Beans, Pinto Beans and Soldier Beans.
Beans for drying are picked when the pods are very dry and the beans rattle inside them.
They need a longer growing season, because they have to be left on the plant longer and in the fall, the growers need to hope for reasonably dry weather so they won’t start to rot.