It’s called Zentangle™. As someone who always believed she could not draw, I’m impressed I can produce these designs. I’ve read that your hand gets steadier with practice, so I have hopes of improving. On the other hand, if I don’t get any better – well, too bad. I’m enjoying it.
You can read more about it at the official Zentangle website or at Tangle Addicts, the website of my teacher, Heather Hartwick-Gladden, CZT.