Aging means growing older. You could say that your glamorous grandparents make aging look easy.
The process of getting older, especially as people reach middle age and beyond, is called aging, and it's also an adjective that describes someone or something going through this process. Your aging French teacher might find it harder and harder to read her own writing on the chalkboard, and an aging motorcycle probably needs to be repaired more often. The verb age, or "grow older," is at the heart of aging, and its Latin root is aevum, "lifetime."