Pas Yisroel or Pat Yisrael (lit:"Bread of an Israelite," he:פת ישראל) products are grain-products that were cooked or baked with the participation of an observant Jew. This must be, at minimum, the ignition of the flame used to prepare, cook, or bake the grain product. In classical Rabbinic Judaism, this requirement is considered restricted to the five classical grains of Judaism - wheat, barley, oats, spelt, and rye. In the modern food-production industry, commercial bakeries may accomplish a status of Pas Yisroel by the use of something called the "Shain system", (named for the inventor, Rabbi Yehuda Shain) whereby an entire apparatus can be ignited remotely by an observant Jew.
It is customary that extra care is taken to uphold this observance during the first ten days of the month of Tishrei, between Rosh HaShanah and Yom Kippur.
The qualification for one to be considered an "observant" Jew – and therefore able to uphold the observance of Pas Yisroel – is defined as one who is Shomer Shabbat. This is regardless of affiliation. As an example of this encompassing multiple denominations, let's use a hypothetical scenario of a Reform Jew who is a baker, and an Orthodox Jew who wants to buy the baked goods produced by the baker; if the baker is:
then the grain-product could still receive a distinction of Pas Yisroel by the Orthodox Jew's preferred Hekhsher.