What's the difference between Vinyl Transfers and regular stickers?

A sticker is printed and cut as one piece, often with a visible edge or background. A Vinyl Transfer is cut out of colored vinyl and applied with transfer film, so only the separate letters and shapes stay on the surface.

How they differ

Both stick to a surface, but they're made differently and used for different things.

Stickers

Your design is printed in full color on a material and cut into a shape, often with a visible edge or background.
You peel it off the backing and stick it on in one go.
Quick and simple, for almost anything: laptops, packaging, giveaways, personal use.
Examples: Die-cut Stickers and Kiss-cut Stickers.

Vinyl Transfers

The design is cut out of solid-color vinyl. There's no print, so each color is its own piece of vinyl and photos or gradients aren't possible.
A transfer film holds the whole design together while you place it.
Once applied, only the design remains. Each letter or shape stands on its own, with no background.
Used where placement matters and the result should look clean and part of the surface: storefronts, windows, walls and branding.
See Vinyl Transfers.

Which one to choose

Choose a sticker if you want full color, photos or a quick peel-and-stick. Choose a Vinyl Transfer for lettering and logos where you want sharp edges and no background. Transfers take a bit more care to apply, but give a precise, professional result.

Terms like die-cut and transfer film are explained in the Dictionary. See also how to apply Vinyl Transfers.