A History of the British Monarchy/Angevin Rulers
The Angevin Kings of England came to the throne on the death of King Stephen. The Anarchy, the civil war between Stephen and the Empress Maud (Mathilda) ended in 1153 when Stephen recognized Henry FitzEmpress, the son of Mathilda, as his heir.
Stephen died in 1154, and Henry became king of England as Henry II.
This dynasty is also called the House of Anjou, and also considered the first Plantagenets. Henry II's father was Geoffrey Plantagenet, Count of Anjou, so those names are equally valid. The name Angevin refers to the fact that during this time the crown controlled more area on the European continent than they controlled in Britain. The area they controlled is referred to as the Angevin Empire.