Who were the Gentiles?

In many gospel readings the "Gentiles" are referred to. Two weeks ago, after more than 20 years of growing up in the Catholic faith I realized that I did not know who they were. Was it a nationality? A religion? what? Turns out my parents did not know either. So, naturally. I thought about it ... then forgot about it.

But for some reason I just remembered it, and happened to be sitting with my computer anyway, so I looked it up. (I used ask.com which took me to the international standard bible encyclopedia). This is what I found:

Gentiles, pronounced jen'-tilz, is commonly used for a non-Israelitish people. The Gentiles were far less sharply differentiated from the Israelites in Old Testament than in New Testament times.

Under Old Testament regulations they were simply non-Israelites, not from the stock of Abraham, but they were not hated or despised for that reason, and were to be treated almost on a plane of equality, except certain tribes in Canaan with regard to whom there were special regulations of non-intercourse. The Gentile stranger enjoyed the hospitality of the Israelite who was commanded to love him and to sympathize with him. They had most of the same rights, earned the same respect, given permission to practice the faith in Jewish temples, and were even allowed to rule over Israelites.

But as we approach the Christian era the attitude of the Jews toward the Gentiles changes, until we find, in New Testament times, the most extreme aversion, scorn and hatred. They were regarded as unclean, with whom it was unlawful to have any friendly intercourse. They were the enemies of God and His people, to whom the knowledge of God was denied unless they became proselytes, and even then they could not, as in ancient times, be admitted to full fellowship.

Jews were forbidden to counsel them, and if they asked about Divine things they were to be cursed. All children born of mixed marriages were bastards. That is what caused the Jews to be so hated by Greeks and Romans, as we have abundant evidence in the writings of Cicero, Seneca and Tacitus...