The lapel is a distinguishing characteristic of a sports coat, blazer, sweater, tuxedo, or suit jacket. Aaron Marino of alpha m. discusses three types are shawl, notched, and peaked.
The shawl is a continuous curve with no cut-outs or points. It was designed and worn with the Victorian smoking jacket. Presently you'll find it with tuxedos and sweaters. You won't find this lapel with suits, sport coats, and blazers.
The notched lapel is the standard in men's suiting: traditional yet contemporary and the most common option. If you are going to have a suit or two, Alpha recommends the notched lapel which can be dressed down and is the most versatile. The notch depends on the lapel width.
The peaked lapel edges are pointed up to the shoulder. You'll find it in tuxedos and suits. You can find it on a sport coat and blazer but it's uncommon as it's the most formal of lapels. It's super sassy and pizazz. This lapel makes a statement.