An asterism in Cassiopeia, formed from 5 stars. Not one of the 88 constellations.
Five stars in a zigzag, opposite the Big Dipper across the pole. When one is low the other is high, so between them something is always available to find north by.
The W is centred near right ascension 1.0 hours, declination +60°. It is circumpolar from most of the northern hemisphere, meaning it never sets and can be found on any clear night.
The International Astronomical Union recognises 88 constellations, and they divide the whole sky between them like countries on a map. The W is not one of them — it is a pattern picked out of Cassiopeia. That makes it an asterism: a shape people recognise and name, with no official standing whatsoever.
The distinction matters less than it sounds. Asterisms are usually easier to find than the constellations containing them, which is exactly why they survive.
SkyRef can draw the W in its real position for wherever you are — switch on the asterism layer and it appears dashed across the constellations it runs through.