Core values

Core values are basic or central values that integrate a culture and help to distinguish it from others.

Core values are defined as the essential, enduring tests of an organization or culture. These very small set of principles to guide and have profound influence on how everyone in that organization or culture think and act. When following these core values, actions require no external justification. These values have intrinsic value and are of significant importance to members of this organization or culture. There need only be a few, but powerful, guidelines for members to follow. These core values define the organization or culture into what it is and what it does. It sets it apart by defining the overall character of the organization or culture. These values give the organization or culture and identity that stays with it. In other words, core values provide the glue that hold an organization or culture together.

See also ethics.

Source
Sidorowicz, Rick. Back to the Beginning - Core Values. The CEO Refresher, 26 November, 2005. 

Core values are words that represent what is core to you and therefore essential to the quality of your relationships and your life. Whether you are aware of them or not, they guide your thoughts, feelings, and actions. Knowing them allows you to use them to your advantage, especially in difficult or challenging situations.

Three criteria distinguish a Core value: (1) essential, (2) universal, and (3) personal.

They are essential because you cannot live without them. For example, if honesty is one of your Core values and you are told that honesty will never happen, ever, you would say, “Then what is the point of life?” It is so fundamental that life would be meaningless without it. This does not mean that it happens all the time, or that you even act consistently with it all the time. Simply said, you cannot imagine life being worth living without it, or at least the possibility of it.

Universal means that your Core values apply everywhere, all the time. This is true whether you are at home, at work, or in line at the movie theater. Let’s say, for example, respect is one of your Core values and you are in a movie line and someone cuts in ahead of you. You will notice it and it will bother you. Depending on the relative importance of the movie, you may or may not take action. At the very least, you will feel bothered. This is an indication that a Core value is being affected.

Core values are personal because they are grounded in your life experiences. This only means that if you and a co-worker both have a Core value of trust, you may describe it differently. Underlieing the descriptions is the same essential value.

For a value to be a Core value, it must meet all three criteria.

World Collegiate Association for the Research of Principles promoting its 4 core values: LIVING FOR THE GREATER GOOD, OWNERSHIP, TEAMWORK, AND DREAM BIG!

Source
Mason, Sean. Core Values Exercise. United Communication Unlimited.