Utilities allow CSS programmers to write consistent, reusable code that's versatile, reusable and flexible. They're small CSS classes that can be used reused across the site, and tweaked where necessary.
A wrapper is a great example. Quite often, we need to contain a site at a max-width so content is readable, and we have a nice padding on smaller devices that isn't at max-width size. Taking our wrapper example, imagine if we needed variations of our wrapper, we could do the following:
This means we're not duplicating the other lines of CSS, keeping our code neat, reusable but the key thing here is also allowing it to be flexible!
Take a look at other utilities baked into Blyth.