What is the policy of Appeasement?

To
"appease" someone is to give in to their demands in hopes of avoiding further and
greater demands and/or in order to avoid having to fight them.  This is what was involved in the
policy of appeasement that was taken by Britain and France before the start of WWII.

Hitler was very unhappy with the Treaty of Versailles and he wanted to do various
things that would violate that treaty.  These involved things like rearming Germany and taking
territory that Hitler felt should be German.  The policy of appeasement consisted of allowing
him to do these things in hopes that he would not do anything worse.

For
example, then, when Hitler wanted to take the part of Czechoslovakia known as the Sudetenland
(because ethnic Germans lived there) the French and British allowed him to do so.  They did this
in hopes that that would satisfy him and a war could be avoided.