Three key aspects of culture that distinguish one cultural group from another are values, norms, and sanctions.
For sociologists, the term values refers to the ideas that people in a culture have about what is valuable or not valuable, beautiful or ugly, good or bad, right or wrong, desirable or undesirable. Our values shape our preferences in life, and we use our values to make choices. To learn about a person's values is to know a lot about that person. Thus to learn about cultural values tells you a lot about that culture.
People of a culture express their values through the norms that they establish and enforce. Norms are rules or expectations for how people should behave in a given situation. There are four types of norms: folkways, mores, taboos, and laws.
Folkways are expectations for behavior that are not strictly enforced. For example, in the United States, when a passage is crowded people are expected to walk on the right side, to include the word "please" in any request they make, and to line up for service in a crowded store. You can see from these examples that "folkways" is in part just a technical term for "manners", in that folkways distinguish polite behavior from rude behavior.
Mores (pronounced "more-ays") are rules for behavior that express core values in a culture, and are thus taken far more seriously than folkways are by people in that culture.. There are always punishments when people violate a more. In the United States, examples of mores might include norms against robbing, killing, or sleeping with the partner of one of your close friends or relatives.
Taboos are norms which prohibit behaviors that most "sane" people in that culture would never even consider, and who would experience feelings of physical revulsion just considering that behavior. Examples in the United States might include taboos against sex with your close relatives, sex with any child or animal, cannibalism, or eating feces.
A law is any norm which is written down in a legal code and enforced by a governmental body. The vast majority of folkways are not written into law, but a few of them are, such as laws against jaywalking or spitting on the sidewalk.
Nearly all criminal laws incorporate mores, such as the mores that prohibit robbing, raping, and killing. However, there are a few mores that are not written into law—such as the jmore against sleeping with your sister's boyfriend. There will be a sanction if you violate that particular more, but it will be enforced by your sister—not the police.
Most taboos are written into law, such as the taboos against incest and cannibalism. However, there is no law against eating feces, even though that behavior is certainly taboo.
Sanctions are a culture's accepted response to a person's violating a norm or conforming to a norm. You can think of sanctions as punishments or rewards.
Positive sanctions are rewards for successfully conforming to a norm. You've received a positive sanction when you get a raise or promotion at work, a congratulatory smile, hug, or handshake, or an A in your sociology class.
Negative sanctions are punishments for failing to conform to a norm. You've received a negative sanction when you are arrested by the police, scowled at by your mother, received the finger from a driver in the next lane, or received an F in your sociology class.