Shema means "Hear", "Listen", and it is the first word of a very important prayer...  

"Hear, O Israel: The LORD our God is one LORD; and you shall love the LORD your God with all your heart, and with all your soul, and with all your might. (Deuteronomy 6:4-5).

Very important for the Jews: The Shema is a confession of faith and summary of the creed of Judaism that adherents to the faith recite each evening and morning, in every feast, in every problem, at the point of death... Martyrs through the ages spoke these words as they met their deaths at the hands of their enemies.

Very Important for Jesus: When Jesus was asked for the First Commandment, he did not answer with the First Commandment of the Decalogue, instead, he answered with the Commandment of the Shema.

Teach it to your children:

Hear, O Israel: The LORD our God is one LORD; and you shall love the LORD your God with all your heart, and with all your soul, and with all your might.  And these words which I command you this day shall be upon your heart; and you shall teach them diligently to your children, and shall talk of them when you sit in your house, and when you walk by the way, and when you lie down, and when you rise. And you shall bind them as a sign upon your hand, and they shall be as frontlets between your eyes. And you shall write them on the doorposts of your house and on your gates.
(Deuteronomy 6:4-9).