It is impossible, in a few words, to sum up Yeshua (Jesus), Who He is, and why He came. The Bible (both the Tanakh [Old Testament] and the Brit Chadashah [New Testament]) testifies abundantly that Yeshua is the Promised One to come, the One Who would be the seed of the woman, the chosen Prophet to God's People, He Who would bear our sins, and He Who will return bringing lasting world peace. The Bible is also very clear that this Promised One would be none other then God Himself in the flesh.
There is One God. He may choose to manifest Himself however He wishes. Many Jews are taught that it is impossible to believe in Yeshua without denying both God and our people, as they see submission to Him tantamount to blasphemy. Since, however, Yeshua is God Himself, no spiritual treason is involved. Very much instead, we would be remiss not to love, obey, and worship Him.
Don't take my word for it. I encourage you to diligently study the Scriptures and seek God about Who this man Yeshua is. Ask hard questions and be open to the hard answers.
Click here to go to a site which will detail for you some of the many, many prophecies which Yeshua fulfilled in His life.