What was the name of the 1st constitution the U. S. had? What is an "amendment" in regard to the Constitution?

The Bill of Rights, which was introduced to Congress in 1789 and adopted on December 15, 1791, includes the first ten amendments to the U.S. Constitution.

A constitutional amendment is a modification of the constitution of a polity, organization or other type of entity. ... Most constitutions require that amendments cannot be enacted unless they have passed a special procedure that is more stringent than that required of ordinary legislation.

the second significant cause of the great migration was the desire of black southerners to escape segregation, known euphemistically as jim crow. rural african american southerners believed that segregation - and racism and prejudice against blacks - was significantly less intense in the north.