What to do if i was just curious how someone can tear their achilles tendon. it seems like it would be very difficult to do. how does it happen?

Not difficult rather: It may be the result of a sudden and great increase in the pulling force on it, rough landing from a basketball jump, pushing a stalled car, etc. It can also be set up by certain medications' side effects. Certain groups of medications are known to occasionally cause weakening of the tendons and cause muscle pain.

It is hard to do: It is usually due to an overstretching or direct trauma of the back of the foot.