Notability points is a useful way of thinking of whether something is notable (and worthy of inclusion) or unnotable (and not worthy of inclusion)
Everything has a certain amount of notability, this can be put on a (rough) scale, from your cat, some really important things like chemistry, Lenin, the Earth, the Sun etc.
There is an inclusion threshold of n "points" where n is an arbitrary number. Let's say it's 100.
In reality, n is not a fixed value. Some things with only 75 points are kept, other things with 125 points are deleted. This is the grey area that everyone argues about. It sometimes seems strange that a reality TV contestant who appeared on a few TV episodes whose fame hinges on a sex tape may be deemed notable, but a Harvard professor with a PhD and 30 years teaching experience may be deemed non-notable.
Points are cumulative, that is, if you get 25 points for X, and 35 for Y, and 45 for Z, then you get 105 points in total.
This means that a number of individually relatively insignificant things can be notable in totalis.
Points can be received for the subject either doing something or having something done to it.
Nothing should be excluded from consideration, and this includes guidelines such as "WP:VICTIM", "WP:NOTINHERITED", where notability for being a victim of a crime or a relative of someone who is notable is downplayed; yet it can and does contribute sometimes.