Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to CuriousKidsUS@theconversation.com. What is Bluetooth? – Henry, age 13, Somerville, ...

While wired headphones have made a comeback among the cool kids in recent years, some of us prefer not to get tangled up in cords. And phone makers have largely dumped the headphone jack on their ...