The two triangular strips of fabric that protrude from the collar of a suit jacket are known as the lapel. Take a look at this article on Lapel.
What is Lapel?
The folded flaps of fabric on the front of a coat or jacket below the collar are known as lapels. They are often created by folding over the front edges of the jacket or coat and are most frequently seen in formal attire and suit jackets.
Left-side lapels have a buttonhole that’s designed to carry a boutonnière, a decorative flower that’s now typically only seen on more formal occasions. The breadth of the lapel can vary greatly on suits, yet some designers insist that the most fashionable lapel width never changes.
Different Types of Lapel
The Notch Lapel is the most popular and universal of all lapels. This style is perfect for blazers, sportscoats, suits, and tuxedos even though it sounds way too hard because the bottom of the collar and the top of the lapel meet at a 75-90 degree angle.
Peak lapels are a more fashionable option that will help you stand out in a crowd.
The Shawl Lapel has no peaks or notches; it just wraps around completely. You will see the most stylish and dapper in this outfit, which is typically associated with tuxedos.