Explain what characterized the Kennedy years.

There could be many answers to this, with different
answers for domestic affairs and foreign affairs.

The most
important thing that characterizes the Kennedy years, in my view, is foreign affairs. 
Kennedy's short term in office was quite eventful in foreign affairs, particularly in
terms of the Cold War competition with the Soviet Union and communism in
general.

There were at least three major events or areas of
importance.  The first two have to do with Cuba.  These were the Bay of Pigs invasion
and the Cuban Missile Crisis.  The third important area was the increasing involvement
in Vietnam.

All of these events had to do with the US
trying to prevent the spread of communist power across the globe.  This Cold War issue
was very characteristic of the Kennedy years.