Kosher food is food that is deemed acceptable for consumption by the Kashrut, or laws governing food, which are found in the Talmud. The reasoning for keeping kosher is not specifically outlined in the texts, but some suggest it is for hygienic or philosophical reasons, whereas some scholars claim that it is simply a test of mans obedience. Either way, about one-sixth of the Jewish population in America keeps kosher, so there is a large need to differentiate between kosher and non-kosher foods.
The main laws for kosher consumption are that meat and dairy cannot touch at any point during the production or consumption process. Kosher also prohibits one from eating pork or shellfish and requires that all mammals and birds are slaughtered in a specific way known as shechita. There are some nuances, of course, but these are the basic principles, with the first being the most difficult to manage in most cases. Think about meat and dairy not being able to touch: no cheeseburgers. However, it is not that simple. Due to the restrictions on production, the meat and dairy can never be on the same counter spaces, touch the same cutlery, or even be washed in the same dishwasher. Many households that keep kosher have separate dishwashers, sinks, and even refrigerators to help them abide by the kosher laws. Overall, it can be a tough process to figure out if you are new to it, or if you are trying to help your friends who keep kosher feel more comfortable in your home.