Surrender value (also called cash surrender value) is an amount of money that you, as a life insurance policy holder, receive if you decide to terminate (surrender) your life insurance policy (e.g. whole life Insurance policy) before it matures or before you die.
A number of life insurance policies, in addition to their life insurance components, also have cash accumulation components (similar to investments accounts) and thus accumulate some value. This value is understood as the (cash) surrender value.
It does not make sense to surrender the policy early, since the surrender value will be quite low compared to the premiums paid.