Reconstruction was the period of time that came right after the Civil War ended. The era was known as "Reconstruction" because it was supposed to be a time of rebuilding. The South needed to be rebuilt physically and economically because the Civil War had destroyed many things in the South and because the system of slavery had ended. It was also a time of rebuilding the nation as a whole. The country had to figure out how and when to reintegrate the Southern states into the US.
During this period, the main issues were 1) how much to punish the South for secession and the war and 2) how much to force the South to respect the rights of the freed slaves.