What is The Liberator?
I assume that you are asking this question about US history. In that case, The Liberator was the name of an abolitionist newspaper that was started by William Lloyd Garrison (a famous abolitionist) in 1831.
Garrison was a believer in immediate and uncompensated abolition of slavery. He did not agree with the idea of paying slaveowners for their slaves and he did not agree with the idea of sending the freeds slaves to Africa to live.
In order to disseminate his views, Garrison created The Liberator. This was a major step in making the views of the abolitionist community more widely known in the US.