You can describe something that's funny, lighthearted, or flippant as joking. A joking manner can be a good quality in a kids' dentist and a not-so-good quality in a funeral director.
A joking birthday card might tease the recipient about his advanced age, and a joking tone in an interviewer's voice keeps the mood light and playful. When you're in a joking mood, you're full of good humor. At the heart of the adjective joking is joke, originally joque, from the Latin iocus, "joke, sport, or pastime."