Protestantism is usually summarised by five Latin slogans, and the summary is useful as long as two things about it are understood: the list was assembled long after the Reformation, and it is not what the Protestant confessions argue with each other about.
Five words, formulated late
Scripture alone, faith alone, grace alone, Christ alone, glory to God alone. Luther and Calvin use the individual phrases, but the five as a set are a twentieth-century teaching device, and no sixteenth-century confession lists them. They describe the common front against Rome accurately enough. They are silent on everything that split the front itself.
The real fault lines
The divisions that produced separate churches are about the sacraments, about church government, and about the extent of the atonement. Luther held that Christ is bodily present in the supper; Zwingli held the meal a memorial; Calvin proposed a third account, and the failure to agree at Marburg in 1529 is the moment Protestantism became plural. Baptism of infants against baptism of believers divided the Reformed from the Anabaptists violently. Whether a church is governed by bishops, by elders or by the congregation produced three more families.
A word that not everyone accepts
Anglicans of the Anglo-Catholic tendency, and many Lutherans, resist being described as a denomination within Protestantism at all, on the grounds that they are reformed catholics rather than members of a movement. The atlas records that disagreement on the link itself rather than deciding it.