Reconstruction is the period from 1865 - 1877 after the Civil War where there was to be some attempt to put the country back together politically, socially and economically. Unfortunately, it was a dismal failure.
While slavery was abolished and blacks were made full citizens with voting and legal rights, these things were not enforced much in the South. About 5% of freed slaves were given a basic education before the Freedmen's Bureau was closed, with the rest illiterate. Blacks received no land and ended up, often times, working for their former masters.
Also, the South was never allocated the resources and funding to rebuild their cities and economies. The long term legacy, besides racism then, was poverty in the South, so that today, 9 out of 10 of the poorest states in the country were in the Confederate States of America.