It was called a civil war because it was fought internally. The US citizens weren't fighting the citizens of another country, they were fighting themselves. The south wanted to secede from the union. The North did not want to lose the southern states. The southern states took over all the government forts in the south.
After Fort Sumter, war had began The south decided to stay in the south and fight on their own turf. The North had an advantage because they had more supplies and people. The first big battle was Bull Run. The south beat the union. The Union navy stopped southern trading ships. There were more land battles and the north was getting its ass kicked.
The two army commanders were Robert E. Lee for the south and Ulysses S. Grant for the north. Lincoln said the war was about saving the country NOT to end slavery. But the north was losing, so to unite the northern people, he made slavery the focus of the war. He issued the Emancipation Proclamation (1862) which said that all slaves are free.
The south was kicking ass. They decided to invade the north. There was a battle in Pennsylvania at Gettysburg. The north won. This was the turning point of the war. General Sherman (union) marched into Atlanta and burned it down. This was bad for the south because they needed Atlanta for supplies and stuff.
In Virginia, Lee’s troops and Grant’s troops fought. The south was losing Lee surrendered the Confederate army at Appomattox, VA. Lee and Grant sorted out a treat at Appomattox courthouse. The war was over Lincoln was elected to a 2nd term. Too bad though; he was shot by John Wilkes Booth, a dude who sided with the Confederates.
Slavery was abolished. The 13th amendment made it illegal