Having trouble grasping what the word 'skill' means.

skill |skil|nounthe ability to do something well; expertise : difficult work, taking great skill.• a particular ability : the basic skills of cooking.

When skills come into play while writing a CV, its like it has to be official, certified for it to count as a skill. So, I can prove I have a clean driving license but saying I am proficient researcher and documenter is measurable... depending on who looks at my CV. BRAIN ACHE.