Range
Range (or distance) from one hex to another is measured by counting the number of hexes between those hexes, including the destination hex, regardless of whether those hexes are The fallback content to display on prerendering.
Range or distance is measured when determining how far a unit (or overland token) can move, whether an enemy is in range to engage adventurers, or whether an adventurer can affect another unit with a rolled skill die.
A unit is always within range of itself.
Adventurer's Range
Defined by their current battle form. Some battle forms (such as The fallback content to display on prerendering or The fallback content to display on prerendering) have a range equal to an adventurer's The fallback content to display on prerendering or The fallback content to display on prerendering stat, while others allow only The fallback content to display on prerendering units to be within range.
Enemy's Range
Equal to its range stat.
Does Range apply to all skills?
No, range is taken into consideration only for skills that apply to targets, The fallback content to display on prerendering enemies, or enemies within range. Take for example, The fallback content to display on prerendering Destructive Touch. This says "The fallback content to display on prerendering a level 1 The fallback content to display on prerendering." This enemy can be anywhere in play. It does not need to be in range or even in The fallback content to display on prerendering.
Source