Answer: A threat assessment is a process of checking all the threat involved in a decision. A threat is what you are protecting from happening.
A risk assessment is the process of checking all the risk involved involved in a decision. Risk is the damages caused by threat to our properties.
It is very important to know the threat involve in taking a decision, because it helps us to evaluate the risk involve. You can't know how to prevent damages to you property without knowing the probable cause of such damage. Because threat assessment tells us what could cause a damage and risk assessment tells us how such damage can endanger us, it is more important to study the cause first, because the possible outcome of the cause.
Threat assessment plays a very vital role, as it helps us to know what causes damage and loss.