You know this one. It's the part that goes around your neck. More specifically, from just over the shoulder where it joins the lapel and around the back of your neck to the other side.
2. Lapels This is the part of your jacket that extends down your chest. The size of a lapel will vary with each designer and brand, but there are three distinct shapes of lapel: shawl (rounded, as on a tuxedo), notched (with the cut-out V shape seen here), and peaked (with pointed tips, usually on a double-breasted jacket). Nowadays, the most common lapels are shawl and notched.
These are the V-shaped notches that marks the place where the collar meets the lapels. The higher the gorge, the longer your jacket will look. (Note: some people, less versed in correct tailoring lingo than us, use gorge to refer to the "V" of exposed shirt between the collar and the buttons when the jacket is done up.)
4. Breast pocketThese are always open and should never come with a — it'll ruin the line of the suit. And the only thing that should go in the pocket is a handkerchief or pocket square.
Think a pocket is just a pocket? Think again. Flap pockets feature an extra piece of material, while slit pockets give a cleaner, crisper line.
The buttons on the sleeve of a suit are nearly always for show, part of the "trimming" of the suit, to use another good tailoring term. Traditionally there are four, but more contemporary suits can have as few as one.