Our English word Patriarch comes from Greek πατήρ (patēr) meaning "father" and άρχων (archon) meaning "leader."  Typically it is used to refer to a senior male member of the family through whom inheritance is counted.  The Patriarchs are the men who begin what will become the nation of Israel. 

Abraham, Isaac and Jacob are the Patriarchs. They are both the physical and spiritual ancestors of Judaism.  It is common in Jewish circles to refer to Abraham as the first Jew.  The terms Jew and Judaism are modern terms of course but they would not exist toady if it were not for the Patriarchs.  That said, if you asked Abraham if he was a Jew I do not think he would know what you are talking about. 

Abram, renamed Abraham — called the father of nations —  is the first of the Patriarchs.  He is called by G-d out of all mankind to become a great nation and through him all nations will be blessed (see Genesis 22.18).  Abrahams story is that of a man who remains faithful to G-d even though it appears that the promises are impossible. 

Isaac— is the son of Abraham who inherits the promise and carries on the line of the covenant relationship with G-d. Isaac has a half-brother Ishmael who is actually Abraham's first-born son but in the Bible story he is not the son of the promise.

Jacob is the son of Isaac.  He is renamed Israel, which means he who wrestles with G-d.  He becomes the father of 12 sons who become the patriarchs of the 12 tribes of Israel.