Use the noun raillery to describe a kind of joking or gentle teasing. There will probably be a bit of raillery between elementary school students on a field trip bus, for example.
If you engage in raillery, you make fun of someone — but lightheartedly, not in a way that would cause offense. The raillery between good friends or siblings might include laughter and teasing, or a joking banter back and forth. To rail is to complain, although its Middle French root, railler, means "to tease or joke," possibly from the Old Provençal word ralhar, "to scoff or to joke."