What does Galatians 2:11 mean?

(for he who worked through Peter in the apostleship with the circumcised also worked through me with the Gentiles);

and when they perceived the grace that was given to me, James and Cephas and John, they who were reputed to be pillars, gave to me and Barnabas the right hand of fellowship, that we should go to the Gentiles, and they to the circumcision.

They only asked us to remember the poor—which very thing I was also zealous to do.

For before some people came from James, he ate with the Gentiles. But when they came, he drew back and separated himself, fearing those who were of the circumcision.

And the rest of the Jews joined him in his hypocrisy; so that even Barnabas was carried away with their hypocrisy.

But when I saw that they didn’t walk uprightly according to the truth of the Good News, I said to Peter before them all, “If you, being a Jew, live as the Gentiles do, and not as the Jews do, why do you compel the Gentiles to live as the Jews do?