ReligionFacts is wrong here. However, I understand why they are using this terminology. Presbyterians are the most prominent branch of the Reformed tradition in North America. Hence, Presbyterians are often identified with the Reformed.
Another inaccuracy is use of the word “denomination” to mean “tradition.” A “denomination” is an organization–there is no one Presbyterian “denomination” much less one Reformed “denomination.”
Originally the Reformed were those Protestants who did not agree with Luther on certain major issues, such as the Real Presence. As the Lutherans closed ranks and excommunicated anyone who rejected certain confessional statements, the Reformed began to do the same thing, creating texts like the Belgic Confession, the Heidelberg Catechism, and the canons of the Synod of Dort (these three are generally known among the Reformed as the “three forms of unity”–i.e., the basic texts that all Reformed are expected to accept). In continental Europe a basic Reformed consensus emerged over against both the Lutherans and the Catholics (or the Anabaptists and Socinians on the other side).
In Britain the situation was more complicated. The Church of England in the later 16th century was part of the broad Reformed consensus, but Anglicans kept a lot of Catholic structures and rituals and resisted overly precise doctrinal definition. So the “Puritan” movement developed, calling for closer alignment with the “best reformed” churches on the Continent. Eventually, after a century of conflict and civil war and all sorts of twists and turns, the Puritans were forced out of the Church of England (though many Anglicans continued to be basically Reformed in theology). Puritans divided into Presbyterians (who did succeed in taking over the Church of Scotland, though they failed in England), Congregationalists, and more radical groups of which the largest and most moderate were the Baptists.
All these groups immigrated to America, of course. The early New England “Puritans” were Congregationalists, but outside New England Presbyterians were more common. In the 1960s, the United Church of Christ was formed from three different groups, two of whom were Reformed in origin: the Congregationalists and the Evangelical and Reformed Church. The “E & R” was itself a merger of two churches: the German Reformed and the “Evangelical Church of the Prussian Union,” which was a fusion of Lutherans and Reformed.
So the UCC is not Presbyterian, but it does draw on two different branches of the Reformed tradition–English Congregationalists and German Reformed. Hence if you’re speaking loosely, I can see why you would call them Presbyterians.
The three main branches of the Reformed tradition as I see it are Continental Reformed (Dutch, German, etc.), Presbyterian, and Congregationalist. Anglicans and Baptists stand on opposite sides of the Reformed tradition but have a similar relationship to it–there are members of both traditions who consider themselves Reformed and others who do not. Both traditions have been deeply influenced by the Reformed tradition but have moved away from it in many ways.