Question

What is fear? And why do we have it?

Answer 1

Answer:

Fear (from a quick Google search): "An unpleasant feeling triggered by the perception of danger, real or imagined."

Simply put, fear keeps us safe (or at least tries to).  It helps keep us on the lookout for things that could be of harm to us.  

Answer 2

Usually of the unknown anything we don’t fully understand we are actually deep down afraid of it. We have it to keep us from taking to many risks as it could be dangerous.