Please tell me what does "complete loss of fiber of the anterior talofibular ligament consistent with a tear" mean?

You ripped up a: Ligament to the front outside part of the ankle. Likely this resulted from a bad ankle sprain or injury. This potentially could cause you pain or ankle instability.

Fiber: This sounds like the description of an MRI or ct scan describing a complete rupture of that ligament. See your podiatrist for assistance as this may need surgical repair and can cause chronic pain and instability.