Re. Pollock: A great deal of discussion on earlier say, pre 20th century painting centred around a painter's 'brushwork'.
From a distance a painting may appear an accurate cohesive realistic portrayal of an object or a person, but from close-up it may dissolve into a series of nothing more than blobs & streaks of paint, see Rembrandt close for example.
With the advent of photography in the middle of the 19th century artists started to turn away more from realistic, 'photographic' depiction, see the 'Impressionists'.
In the early 20th century some artists even eschewed any form of representation at all, and concentrated on pure form and colour.
It could be argued that Jackson Pollock in fact returned to the considerations which had surrounded 'brushwork', but without the representation & without the even the BRUSH, -- pure paint and colour applied by gravity alone.
Observers of Pollocks paintings, though there is no overt representation intended, oddly enough, see all kinds of images within marks on the canvas. What can then be a revelation to the open-minded observer is that a painting doesn't have to depict something to have a satisfying appearance (I carefully avoid using the word beauty !)
What can be truly exiting though, is that a person having accepted these criteria may (just may) look then at the world in a different manner, taking pleasure in seeing shapes & colours in say, tangled undergrowth, or the patterns formed by rain on a window pane, things which don't 'represent' anything, they simply ARE.
As with all art forms though, the viewer has to be prepared to give something of themselves to the work in order to gain anything from it.
here endeth the second lesson.