Who they are:
Judaism: Decendants of a man named Isaac, the son of Abraham and his wife Sarah.
Christianity: Generally Gentiles - not decendants of Abraham
Islam: Originally decendants of Ishmael, the son of Abraham and his wife's servant.
Judaism: The Torah, Nevi'im (Former Prophets), Nevi'im (Latter Prophets), Khetuvim - these are the same 39 writings that are included in the Christian Bible's "Old Testament"and were written by ancient prophets and kings who lived prior to the year 0 BC/AD
Christianity: The Bible - the Old Testament (the same 39 writings as the Jewish scriptures) and the New Testament (a collection of 27 letters and writings by the disciples of Jesus). These were written between 30 and 100 AD.
Islam: The Qur'an - the writings of the Prophet Muhammad based on teachings he learned in a vision from God. The Qur'an contains many of the same elements as the Jewish and Christian scriptures.
Beliefs about God
Judaism: God (Yahweh) will send a messiah or savior to save the Jewish people. Jesus was not this messiah.
Christianity: Jesus was the messiah and was meant to save all people, not just the Jews, and from their sin, not a physical saving. He was also the son of God (Jehovah) and rose from the dead.
Islam: Jesus was the messiah but was a prophet, not the son of God (Allah). Jesus did rise from the dead.