Chopsticks is a term that describes anytime the yo-yo is mounted between your pointer finger and thumb.
The most common chopstick mount is a Thumb Mount. From a trapeze, stick your non-throwhand thumb by the string on the yo-yo side of the loop. Swing the yo-yo off the trapeze and land it onto the segments of string between your thumb and pointer finger.
Chopsticks style tricks were invented by Jason Lee, and in 2004, he won the Trick Innovator of the Year award for it. The concept of chopsticks was first presented to the community by Jason in a video called The Fidget, which was produced by Spencer Berry.