What is a thumbnail sketch, and what is its purpose?

Thumbnail sketches are often sketches done by an artist. They are quick and fast with no fixes or changes involved in it. A thumbnail sketch is used to get the basic concept or idea of the sketch. For example, if the artist feels like creating a drawing, the artist very well might create a few thumbnail sketches to get more of an idea that they want to draw. They also may do a thumbnail sketch to see how they want objects in their piece to line up.            

this gave me 100% on ed2020, so I hope it is useful to others.

like any other technology, art form or field, digital cameras have their own nomenclature. the alphabet soup of jargon can be as confusing and intimidating as trying to understand how all those dials, buttons, levers and menu options affect the pictures and videos that you capture. fear not, because we've defined the most important words, phrases, commands and options you'll need to know when shopping for and learning to operate your new dslr, mirrorless, smartphone or other camera.