Similarity between Islam, and Christianity and Judaism:
All three religions are broadly monotheistic, i.e. they believe in the existence of a single god. In Islam, they call it Allah.
In Christianity it is Jesus, and in Judaism, they call it Hashem.
Difference between Islam, and Christianity and Judaism:
Islam states that Prophet Muhammad was the last Prophet sent by the god, whereas, Christianity states that Jesus was the last Prophet and was himself the son of God.
Judaism states that there was no Prophet but only the patriarch Abraham.