This stretch involves the flexor carpi ulnaris which runs along the lower half of your forarm and the flexor digitorum superficialis which connects the wrist to your hand.
Don't ever under estimate the importance of stretching and the benefits it holds.
The Finger stretch is helpful with tennis, golfer's and thrower's elbow, wrist sprain, dislocation and tendonitis, carpel tunnel and ulnar tunnel syndrome.
Always rememberthat while stretching may be recommended to aid recovery out of injury, you should always be very careful when stretching through rehabilitation. Your soft tissues are likely to be more vulnerable to re-injury if you stretch too much or too hard during this time. Always check with your Health Care Professional who is guiding you through your recovery to make sure it is appropriate to start stretching, and please - ALWAYS FOLLOW THE RULES FOR SAFE STRETCHING (The first posting on this stretching blog).
Image taken from "Upper Body Stretches" wall chart by B. Walker.