Skills are the things you do well. Developing an awareness of your own skills allows you to evaluate potential careers. If you choose a field where you excel, your job satisfaction will be higher, you'll have a greater range of openings to choose from, and you'll have more leverage to shape your own work.
There are two types of career skills: transferable skills and specialized knowledge. Transferable skills are useful anywhere. Some examples are verbal and written communication, problem solving, facilitating groups, delegating, and organizing. Specialized knowledge can only be used in a few environments. For example, marketing theory can only be used in the marketing field, and fluency in Estonian can only be used in Estonia or in a corporation that does business in Estonia. Specialized knowledge can only be used and applied through transferable skills.
Unlike your values or your personality, your skills are not set. You develop new skills each day. Skills are highly influenced by your interests, although what you are good at is not necessarily what you like to do, and vice versa. Nonetheless, the two often go hand in hand. If you are interested in a field, but unskilled at it, you can always learn.
If you need help assessing your transferable skills, speak with a career advisor during drop-in advising or enroll in ASCS Q294: Basic Career Development. O*NET also has a skills module that will suggest careers based upon transferable skills you feel you possess.