In UK terms with US equivalents noted in the pattern.

From the webpage:

“I designed these little hanging decorations to add some colourful, homespun Hooky Goodness to my Christmas Tree this season, but there’s no reason why they can’t be used all year round and in all sorts of ways. I’ve had suggestions for using them as baby rattles, baby mobiles, as tags on wrapped gifts, or simply just as little decorative gifts to pass on to friends and family.

These are quick and satisfying little things to work up, ideal to use up those little itty bits of stash yarn that you might have lurking somewhere. I personally prefer to use cotton yarn for making decorations (here I’ve used Rico Creative Cotton), but any yarn would be fine. I also tend to switch down a hook size for making decorations which keeps the stitches quite tight and prevents the polyester stuffing showing through the gaps. So for example where the Rico cotton suggests a 5mm hook size, I switch down to a 4mm hook.“