The definition of "reformation" is that it is the act of improving or changing someone or something. Many people and things undergo reformation. People with destructive vices undergo reformation when they try or someone else tries to bring about an improvement or a change. Government undergoes reformation when caught in corruption, such as the political reformation of Tammany Hall when that government-linked corruption became intolerable.
If you mean the Protestant Reformation ushered in and led by Martin Luther, the effort was to improve and change the religious strictures of false dogma that were imposed upon Christians by the Catholic Church, which, before the Reformation, was the only Christian Church in Western civilization (Eastern Orthodoxy held sway from Constantinople to the east and northeast in Christian lands). A primary point of reformation in the Reformation was the practice of purchasing forgiveness from sins through Indulgences. Another was the doctrinal dogma that a priest was needed to facilitate commune with God.