Okay, give this one a try: Put one hand flat on the table. Lift the palm of your hand up so only your finger and thumb tips are touching the table. Now bend your middle finger under so half of your finger from big knuckle to joint near your nail is pressed really hard down on the table. Now in turn lift your thumb, then your index finger, and finally little finger. No problem, right? Now try the ring finger. Impossible!
Why? The tendons in your fingers are independent from one another apart from the ones in your middle and ring finger. These tendons are connected, so that when your middle finger is folded down you cannot move your ring finger. It feels like your ring finger is stuck to the table! Good party trick ...