Obviously the saving of one Jewish community in ancient Persia is not what makes the joyous Purim holiday so significant. The tale of Purim is important because it provides us with a view of the archetypical villian, Haman. And recognizing the sly Haman who wants to destroy us is important, because there seems to be a Haman in every generation. The triangular pastries are traditionally filled with poppy seeds. Yup, the seeds of the opium poppy.
Some people prefer other kinds of pastry fillings.
On Purim, we dress up our kids in costumes and send them to knock on the doors of our friends and neighbors. They bring a plate of food treats to give to the people whose doors they knock on. This Purim custom is a way of letting our fellows know that we are celebrating the survival and continuity of the Jewish people and a way of expressing our love of our neighbors.