Buttonholes can be used to make buttonholes for buttons, but they can also be used for a decorative element - make a row of them and insert ribbon through them. Super cute! I've also used button holes for curtain hooks, for a drawstring/casing, and to reinforce holes I've cut for purse feet and magnetic closures.
Buttonhole attachments vary greatly from machine to machine. I've included some links that may be of help. Don't be intimidated by this foot! Watch the videos below and practice, practice, practice.
BERNINA: Automatic Buttonhole Foot #3
JANOME: Janome Accessory Tutorial - includes videos for lots of attachments. Here is a guide to the basic Janome Automatic Buttonhole Foot R. And here's another handy-dandy tutorial for the 11000.
HUSQVARNA-VIKING: There a few - The Buttonhole Sensor Foot and the Adjustable Buttonhole Foot. These website are really basic, though - no instruction.
Here is a great tutorial from Sewing With Niler! She's got some GREAT tips!
Want to learn how to sew on perfect buttons? Check out the video below: