In the simplest terms, Messianic Judaism is a movement which provides an environment where both Jewish and Gentile (non-Jewish) believers in Yeshua (Jesus) worship the Lord together in the original Jewish context of the faith.
Historically, the first believers in Yeshua, the Messiah of Israel, were Jewish. For the first several hundred years, this was primarily a Jewish faith. At first, the question was: can non-Jewish people be received into the fellowship of believers? And if so, what do they have to do? Do they have to take on a Jewish lifestyle? Be circumcised? Observe the dietary laws? As the early synagogue leaders sought the Lord's direction, He instructed them to allow Gentiles who would come to faith in this Jewish Messiah to become full participants in this new form of belief known as TheWay. Some people did try to put heavy conditions on Gentile believers, and these were chastised by the Rav Shaul (Apostle Paul) and called "Judaizers". God clearly wished for people to be exactly what he had created them to be, but sanctified by the atoning blood of Messiah. Jew remained Jew, and Gentile remained Gentile. For many hundreds of years the majority of believers were Jewish, and this faith was recognized as a sect of Judaism. The Jewish way of life continued to be the basis and mainstay of the life of the Messianic believer. Yeshua Himself walked in the ways of His people, flawlessly observing and fulfilling the law.
However, over time, this has changed. For many reasons (which we will not go into here), the situation became quite the opposite. Jewish people coming to faith in the Messiah of Israel have been told they must "convert" to a new religion: Christianity. In most cases, doing this means joining a church, moving away from the Jewish way of life and embracing a whole new religion and lifestyle. The children of such "converts" are not raised according to the Jewish laws and customs. For all intents and purposes, the Jewish lineage is lost to that family. From that generation forward, they are no longer considered Jews, but Christians.
But in these last days, as God is lifting the veil from the eyes of the Jewish people and they are receiving Yeshua as their Messiah and Lord, He has raised up Messianic Judaism to provide an environment wherein a Jew can come to belief in Yeshua and still remain a Jew. In fact, like most Messianic Jews that we know, I have found that I am learning more about my people and the Jewish way of life, the festivals and holidays, and their true meanings, than I ever knew before I embraced Messianic Judaism. I feel connected in a deep and profound sense, through my Messiah, through the thousands of years of Jewish history, to King David, to Abraham, Isaac, and Jacob.
So, what is a Messianic Jew? A Jewish person who has come to faith in the Jewish Messiah of Israel: Yeshua ha Meshiach, (Jesus the Christ, the Anointed One of God), and who practices that faith in its original Jewish context.
And what is a Messianic Gentile? A non-Jewish person who has come to faith in the Jewish Messiah of Israel, and who has received a calling from God to come alongside the Jewish people and worship in a Messianic congregation.
Whether Jew or Gentile, Messianic believers trust solely in the shed blood of Yeshua to be the atonement for our sins. We know that He is the only way to the Father. And we come together, from all tongues and tribes and nations, to worship the Lord in spirit and in truth. Yeshua said that His Father's house would be a house of prayer for all nations, and in Messianic Judaism, we are seeing this become an exciting reality!