Learn English – the difference between “dream” and “ambition”

I think the difference here boils down to the differences between these words:

• need (require)
• want (desire but do not need)
• whim (sudden or random desire)

The original quote is saying that context is a need, not just a want. When discussing requirements it is normal to prioritize according to needs and wants. That is the distinction that the author is making here.

A whim, on the other hand, is not as strong a desire as a want, and using the word "whim" softens the nature of the desire for context. Thus, the author wanted to keep the word "want" for its specific purpose in this context.

Both words have senses that match:

• skilled, “Having or showing skill; skilful”
• skillful (or skilful), “possessing skill, skilled”

but skilled has an additional sense as well, “Requiring special abilities or training”, as in (e.g.) “She works in a skilled trade”.

“He is skillful” can stand alone as a sentence that indicates a person has abilities (either generally or in some area under discussion). I'd not expect to hear “He is skilled” as a sentence by itself, but would expect added detail: e.g., “He is skilled in the martial arts.”

“They are skilled musicians” implies they are able to perform music in a skilled manner. “They are skillful musicians” suggests to me that they have good musical skills and are adaptive or flexible.