We are all in some measure competent within our own cultures - although we all also have days when we feel anything but competent. This ability to understand the structures, habits, customs, and constraints of our own cultural system allows us to accomplish the tasks that we need to undertake to get through each day: To stop at red lights, to wear clothing appropriate to our age, gender, and position, to know when it is our turn to speak in a conversation, to order food at a restaurant. Each person who has grown up within a culture has acquired at least much of the skills and knowledge needed to function within it but - and here is the catch - most of this learning has been done tacitly, without our even being aware of it. We simply learned the myriad facts about our culture as we grew up immersed in it in the same way that babies learn to speak the language of their parents.
This implicitly arrived-at level of cultural competence tends not to be a problem so long as one interacts only with other members of one's own culture (or subculture). However, when one begins to interact with members of other cultures one is all-too-likely to find oneself in a situation in which cultural differences between people lead to misunderstandings and conflict. Such conflict is less likely if one is aware of the ways in which one's own culture affects the way one views the world. In other words, if one is culturally competent, one is likely to be better able to communicate with and work with people from other cultures.
A hypothetical example will help to clarify this concept. Let us take the case of an individual who has grown up in a small, racially and religiously homogeneous town. This individual is quite competent within their own world: She knows the rules of her community. But she is not fully culturally competent because she has no sense that these are in fact the rules of her community: She believes that people everyone act in the way she ...