What is a sketch?

uno boceto es un tipo de borrador, donde dejamos ver los rasgos mas relevantes en nuestra idea grafica

I like what you said when you commented (a sketch is like a really rough draft of the mood and tone) I also sketch alot to find an idea of exactly what I want and I think that is what a sketch is .... experimenting with an idea... but I think we all agree a sketch is not yet the finished project whether you finish that project or get ideas from the sketch.
AND THAT is the beauty of art.

I would agree with the idea that sketch is all about own perception and, let's say own declaration (presentation)... either in creator's or audience opinion.