KSA
Summary
KSA is an acronym for knowledge, skills, and abilities.
Notes
Knowledge
The theoretical/book understanding of a subject.
One can have read a book or seen a video on Judo, but it won't help you much when you need it.
Skill
The proficiencies developed through knowledge transfer as training and/or experience. By going to the dojo, you'll learn Judo. But note that without the theory, you'll probably miss the way it all works together.
Ability
The quality of being able to do something.
There is a fine line between skills and abilities.
Most people would say the differentiator is whether the thing in question was learned or solved, using prior non-related knowledge (ie, using their dance skill to survive a bout).
Attitude
Finally, often forgotten, is the glue that holds all together: Attitude. Attitudes can positively or negatively influence a person's behavior, and therefore level to which they apply their KSAs. In addition it can influence the environment, affecting the application of other people's KSAs.