The line where the imaginary starts to become reality.

There is always a creative feeling when you are holding a pencil, as it gives you the freedom to illustrate what’s in your mind. By means of drawing rough lines and shapes, you begin to use creativity to explore interesting concepts and focus on optimal solutions. A sketch is the moment of genesis of every design.

sketch (noun) = a simple, quickly-made drawing that does not have many details.

^{according to https://dictionary.cambridge.org/dictionary/english/sketch}

It has the word simple in the definition, yet many people are reluctant to sketching. Most of the times, their mind frame is anchored in the idea that they don't know how to draw... But ...