The English Reformation was the process by which Catholicism was rejected as the state religion of England and replaced by the Church of England. In contrast to the Reformation on the continent, the English Reformation was largely driven by the most powerful people in the land. It was not a grassroots movement like the Reformation was on much of the continent.
The English Reformation came about because of the political needs of King Henry VIII of England. Famously, Henry wanted a divorce from his wife, Catharine of Aragon. The reason for this was their failure to have a son together. Henry needed a son to secure the succession and therefore petitioned to have his marriage annulled. This was fairly common at the time (among royalty), but the Pope was politically indebted to Catharine’s relatives and rejected the petition. This caused Henry to break with the Church.
Henry may have also been motivated by a desire for greater control of the Church and its wealth in general. The Church had always been a power center not necessarily controlled by the Crown. Henry felt it was in the Crown’s interests to dominate the Church. He was also happy to destroy British monasteries and reap the economic benefits of doing so.
The Reformation started with Henry, and can be said to have ended more than 100 years later in the Glorious Revolution. It proceeded in fits and starts after Henry’s death, with some monarchs trying to move back to Catholicism and then with the rise of Puritanism. However, the English Reformation did end up with a state church controlled by the Crown to some degree.