The four ministries in George Orwell's 1984 are the Ministries of Truth, Love, Peace, and Plenty. They are all named for positive values that are meant to be beneficial to society, but, in reality, they function to serve the opposite value for which they are named.
The Ministry of Truth is in charge of information as it is received by the public. This information can come in the form of education or art or news or entertainment. Though unbiased, truthful information is the most valuable kind in a democratic society, the Ministry of Truth does not have the ideals of democracy in mind as it works to disseminate only propaganda.
The Ministry of Love is in charge of any activity that relates to maintaining loyalty to Big Brother. Brainwashing techniques than coerce the public's cooperation as well as various systems of oppression are the responsibility of the Ministry of Love. This ministry's misnomer is a truly dark one as torture, grief, confusion, and a general sense of suffering is its aim.
The Ministry of Peace is in charge of anything to do with national security, warfare, and the two armed forces that serve as Oceania's military: the navy and the army. Though it is named for peace, because Oceania is always at war with Eurasia or Eastasia, a more apt name would be the Ministry of War.
The Ministry of Plenty is in charge of Oceania's version of an economic marketplace. Because the society operates within a rationing system, the Ministry of Plenty is not the generous agency that the name suggests. Rather, this ministry keeps members of society poor and in a perpetual state of wanting; this way, they are easier for Big Brother to control.