To some older folk the word "Chesterfield" means sofa, any old sofa; but to the rest of us, it's that particular type of leather sofa with the curled-over arms and the distinctive, tufted upholstery. What's amazing is just how many components go into the thing: Rip one apart and you'll find a wooden frame, several types of metal springs, fabric straps, stuffing between the springs, foam inside the cushions, the leather, the buttons, the thread to hold those latter two together, and tons of upholstery tacks and staples.
We will of course save you the trouble of having to find a Chesterfield you can rip open. While no one online spells out exactly how they're made, I've found two excellent videos that really give you a sense of how they come together, and in what order. The first vid, from the UK's Saxon Leather Upholstery, shows things happening at a factory pace:
This second video, from Italian furniture manufacturer Berto Salotti, shows two old-school craftsman going at it mostly with their fingers. The narration is entirely in Italian, but as in the first video, your eyes are all you really need to figure out what's going on.