These are all just different ways to order hands. An ordering allows you to quickly pick a top 80% range or top 40% range. Unfortunately, there is no unique ordering for defining "top". So these all define top in different ways. Vs Random Hand ranks hands by their equity vs a 100% range. Nash push ranks hands by the order in which they are added to a nash open-shove range as stack depth decreases. Similarly, Nash call ranks them by the order in which they are added to a nash calling range vs open-shoves. Lastly Skalansky-Chubukov ranks by what order hands are added to the S-C open-shove range (in case you don't know, the S-C open shove hands are hands you can open-shove face up at any given stack depth--ie no matter what range villain calls, open-shove is more profitable than open-fold for every hand in the S-C shove range for some fixed stack depth).