What was the Trail of Tears?

Answer 1

The forced movement of Indians out of the south -apex

Answer 2

In 1830 President Andrew Jackson signed into law "The Indian Removal Act" which allowed or authorized the removal of the "Five Civilized Tribes" (Cherokee, Choctaw, Muscogee (Creek), Chickasaw and Seminole) to "Indian Territory" (modern day Oklahoma).
In 1831 combined army, militia, and volunteer forces began to move these tribes along one of several routes to two forts located in Indian Territory: Fort Gibson and Fort Townson. The last tribe moved were the Cherokee in 1838. It should be noted that some tribes accepted bribes of money and or lands, while others did not and were forced under the threat of death - some of these rebelled resulting in armed conflict. During the move there were several way stations along the route, but not all had proper provisioning. For various reasons (from bad planning or indifference to intentional lack of concern, to malfeasant action), many Indians were not allowed or given access to proper food, medical supplies, warm clothing, nor allowed to rest for any significant period of time, which resulted in the deaths of many tribal members. These deaths were exacerbated by the untended dead left along the trail.
The native Americans began to call this trail or series of trails, the "Trail where they Wept / Cried" and it has been changed a little to "The Trail of Tears" by modern translation. The Arkansas Gazette quoted Thomas Harkins (a Choctaw) as saying "[it was] a trail of tears and death"
There were approximately 11 of these trails, taken by different tribes based upon location. They ranged in distance from 200 to 900 miles and went through 14 states (These distances do not include oversea travel):

• North Carolina
• South Carolina
• Kentucky
• Tennessee
• Georgia
• Alabama
• Louisiana
• Florida
• Texas
• Oklahoma
• Arkansas
• Missouri
• Mississippi
• Illinois

NUMBER OF DEATHS
The number of dead are only estimates, as there was no accurate count taken:

• Choctaw: 2,500 to 6,000
• Muscogee (Creek): No estimate
• Chickasaw: No Estimate - paid $530,000 dollars
• Cherokee: 4,000 to 15,000

SEMINOLE WAR
The Seminole resisted movement and started a 'minor' war with the US. The first detachment of 110 US soldiers sent to move the Seminole were attacked and 107 were killed. The government marshaled 500 soldiers against the Seminole and the war lasted for 10 years, costing the US Government 20 million dollars. The US eventually gave up hunting through the swamps of Florida for stragglers. There are no other estimates of dead, on either side.

INCLUSION OF SLAVES (Negro slaves):
African American Slaves either as freedmen, as members of the tribes by marriage, or as slaves of the Indians, were forced to move with the Indians at this same time. The inclusion of these families led to the current conflicts of "[the] Freedmen" of the Cherokee nation.

*Please note that this is not intended to be an all-inclusive answer, it is a basic answer to the questions on the subject and could be expanded into a very large book.