I'm guessing that you're referring to eating Matzoh, and refraining from leaven for the full 7 days of Passover.
The exact details are quite lengthy and technical. Very briefly, the Jews received a detailed command from G-d to celebrate Passover this way during the actual exodus from Egypt (around 3300 B.C.), and included in this command were the instructions to repeat it every year on these days.
Irish Jews celebrate Passover the same way as Jews all over the world.
The same way that all other Jews observe Pesach (Passover).
There are always Jews who celebrate Passover regardless of the location or circumstances. Jews celebrated Passover in the ghettos, and then in the concentration camps.
Yes, because Passover is a Jewish festival. see also:What_do_Jews_do_when_celebrating_passover
Passover is usually only celebrated by Jews
German Jews celebrate Passover, too.
Jewish people celebrate Passover to celebrate their people's liberation from slavery. The holiday celebrates when Jews were freed from slavery in Ancient Egypt.
Jews still celebrate Passover to this day.
There is no such thing as a "reformed" Jew. It is called "reform Jew". Reform Jews celebrate passover as a commoration of the exodus of the ancestors of the Jews from Egypt and into freedom, which is the same meaning passover has to Conservative and Orthodox Jews.
the event they celebrate passover is exodus
The seder has evolved over time. Plus, sacrifice cannot be offered without the Temple so no sacrifices are involved in the Passover celebration.
a passover would be the closes thing...