What does "Kosher For Passover" or "Kosher For Pesach" mean?
First off, the word "Kosher" is the English translation of the Hebrew word "Kasher" (also "Kasher" in Italian). In Yiddish, the word is "Kosher"; in French: "Kascher", and in German: "Koscher". As an adjective, "Kosher" means either "(that which is) fit", "(that which is) fitting", "(that which is) ritually pure" or "(that which is) proper" in Hebrew, in that something or someone - most often food, but also a person - conforms to Jewish religious law or to the Jewish dietary laws in Jewish religious law in the case of food. In Jewish religious law, known as Halakhah or Halachah in Hebrew, Kosher For Passover or Kosher For Pesach (Pesach is the transliterated Hebrew word for Passover) means that a product - whether edible or non-edible - conforms to the specific dietary laws for the Passover or Pesach festival. There are Kosher laws and there are Kosher For Passover laws. Generally-speaking, Kosher For Passover laws include Kosher laws but have added restrictions to the Kosher laws, making them laws that are strictly used and applied during the Passover or Pesach festival.
The principle restriction in the dietary laws for Passover or Pesach is that the product - whether edible or non-edible - must not have any trace of chametz ("leaven" in Hebrew) in it. Chametz includes the five rabbinically forbidden grains for Passover/Pesach: barley, oats, rye, spelt, and wheat - as well as anything that is derived from or includes any one of those grains. The exception to this rule is matzo, which by Jewish law must be made from one of the five aforementioned grains - barley, oats, rye, spelt, and wheat. Since one uses one of the five aforementioned grains to make matzo ("Unleavened Bread" in Hebrew), to keep matzo unleavened and therefore, fit for use during Passover/Pesach by Halakhah or Jewish law, meaning kosher for Passover or kosher for Pesach, one must complete the entire matzo-making process - from the time the grain comes into contact with the water up to and including the completion of the baking of the matzo - within 24 minutes (in practice, most Jewish people follow the authoritative rabbinical opinion to limit this time to within 18 minutes).
"Regular" kosher for Passover or kosher for Pesach matzo uses the flour of one of the five aforementioned grains, and this flour was watched by the supervising rabbi only from the time it came into contact with the water to make the matzo dough. There is also a type of matzo that uses comparatively stricter guidelines with regard to the quality control for the five rabbinically forbidden grains, and this matzo is known as Shemurah Matzo or Shmurah Matzo, meaning "watched" matzo in Hebrew. With Shemurah matzo, the supervising rabbi watches the grain from the time it is cultivated or harvested until the time it comes into contact with the water to make matzo to ensure that no water or other liquid comes into contact with the grain that is used to make matzo. Although both types of matzo use one of the five rabbinically forbidden grains that are at least watched from the time the grain comes into contact with the water until the end of the matzo-making process, the extra level of quality control for the grain used in making Shemurah matzo assures a higher level of confidence in the final matzo product being kosher for Passover or kosher for Pesach.
In addition, kosher for Passover or kosher for Pesach matzo must be made with water that was drawn from a spring I.E. cold spring water, and this type of water must be allowed to settle, be filtered, and then stored and kept cool overnight to room temperature. No tap water or bottled spring water can be used to make matzo. The flour for the matzo, once produced, must of course be completely dry and also stored overnight in a dark, cool space. Both the water and flour must also be watched by the supervising rabbi to ensure no other ingredients or liquids come into contact with the flour or water until the matzo-making process has begun. All this is done so that the rate of leavening or fermentation will not be increased, which would mean that the entire matzo-making process would have to be completed in an even shorter period of time than just under 18 minutes.
As the Passover or Pesach festival approaches, the Jewish food industry creates food and beverage products that conform to these specific dietary laws for Passover or Pesach to make products Kosher For Passover or Kosher For Pesach. They do this by having a rabbi or rabbis from a reliable rabbinical council or assembly or agency supervise and examine the product from the beginning to the end of the product's production. At the end of the product's production, the rabbi confirms that the products are free from chametz ("leaven" in Hebrew). After these products are certified by a rabbinical council or assembly or agency, usually the rabbinical council or assembly or agency that has religious jurisdiction in the city or region where the product was created, a certification label is affixed to the product which states either Kosher For Passover or in transliterated Hebrew, either Kasher le Pesach or Kasher l'Pesach. The certification label also contains a logo in the form of a symbol of the rabbinical council or assembly or agency, along with its name in Hebrew as well as the words Kosher For Passover (כשר לפסח) in Hebrew. The same goes for non-edible products: since they may contain materials that are not Kosher For Passover, the materials that make up the product must be supervised and examined from the beginning to the end of the product's production and then approved by a rabbi from a reliable rabbinical agency, council, or assembly, and then be certified as Kosher For Passover by the rabbi's rabbinical agency, council or assembly, with the Kosher For Passover certification label from that organization being affixed to each product. In order to determine a reliable certification label that indicates either Kosher For Passover or in transliterated Hebrew, either Kasher le Pesach or Kasher l'Pesach, it is best to ask your rabbi which Kosher For Passover, Kasher le Pesach or Kasher l'Pesach certification label to rely on.
A product that has the capital letter "P" labelled on it - from a Kosher For Passover or Kosher For Pesach point-of-view - indicates that the product is both Kosher For Passover or Kosher For Pesach as well as kosher for the entire year.