It's tough to get a sense of size beyond what we can directly observe. An elephant is big. Mount Everest is big. Shaq is big. You can stand next to any of these and marvel at them. Our brains aren't built to think past what we can reliably compare. It's why we use tropes like "the length of two football fields" or "the size of Rhode Island" to sum up things like aircraft carriers and asteroids.
You really can't use those types of measurements with VY Canis Majoris. It's a star in the Canis Major constellation, which represents a dog following Orion the Hunter. VY Canis Majoris needs a whole host of summations. You've got to conceive of it by pieces.
First, the Earth. 40,000 km around at the equator. It'd take you about three years to walk around the entire thing.
The Earth's star, Sol, is 109 times that circumference. A good way of looking at it is to imagine how many Earths could fit inside our sun were it hollow: about a million, give or take. It'd take you about 350 years to walk around the entire thing.
The Sun is a medium-sized star, pretty much smack-dab in the middle of the stellar range. VY Canis Majoris is the largest star we've ever observed, by an absurd magnitude.
Just to give you an idea of this monster, here's it compared to the Sun:
You can't even see it without that handy-dandy magnification.
It would take you SIX HUNDRED AND FIFTY THOUSAND YEARS to walk around the entire thing. If you put VY Canis Majoris in the middle of our solar system, where the Sun is now, it would extend out past SATURN.
Light travels 186,000 miles per second, meaning that it could circle the earth eight times in one second. Light emitted from VY Canis Majoris takes EIGHT HOURS to circle the entire thing.
I'm fascinated by this absolutely beastly collection of superheated gas and matter, as all people are fascinated by the Biggest and Most and Greatest. It's 5,000 light years away from us, fortunately too far away to affect us when it goes...supernova? It's got to go more than that. Hypernova, maybe. A whole new category for the biggest Dog we know of.
Infinite space removes grandiosity's shackles. There is so much for us to discover.