Its story
The Ebionites are first mentioned by Irenaeus of Lyon around 180. Their name probably comes from the Hebrew ebyonim, 'the poor', a title of piety in Jewish tradition. Some Fathers (Tertullian, Hippolytus) speak of a founder called 'Ebion', but most historians consider this figure an invention inferred from the name.
According to the sources, they were Christians of Jewish origin who kept circumcision, the Sabbath and the Law, regarded Paul as an apostate from the Law, and used a single gospel (associated with Matthew; the Fathers quote a 'Gospel of the Ebionites'). They saw Jesus as the Messiah, a righteous man chosen or adopted by God at his baptism. Origen and Eusebius distinguish two groups: one denied the virgin birth and the other accepted it, though without admitting Christ's pre-existence.
Everything known comes from authors who rejected them, and their descriptions (especially Epiphanius' in the 4th century) sometimes blend different groups, so it is hard to know how uniform they were. For the wider Church the answer was the same as to other 'low' Christologies: the confession of Christ as the eternal Son made flesh, and acceptance of Paul and the four Gospels.
The Ebionites vanish from the sources around the 5th century. Historians are interested in them because they show that forms of Jewish Christianity kept the Law long after the apostolic generation, and because of the question of their relation to the Jerusalem community led by James; that link is much debated and cannot be taken as established.