The word historical describes anything related to the past, to history:
We need to consider the current conflict from a historical perspective.
The city center contains many cultural and historical monuments.
I love reading historical fiction.
Historical things can be important or unimportant.
The word historic describes things that were very important or influential in history (or a current event that will likely be regarded as important in the future).
The army's historic victory was the turning point in the war.
Apollo 11 was the historic spaceflight that brought the first humans to the moon.
This is a historic treaty - it is the first time there has ever been a peace agreement in the region.