McDonald's yellow arch shapes are called the Golden Arches.
The arches began as architectural features of McDonald's early restaurant buildings rather than as a purely graphic logo. Architect Stanley Clark Meston designed the distinctive arches for the company's 1953 restaurant in Phoenix, Arizona. The two curved structures were visible from the road and helped the restaurants stand out to passing motorists.
As McDonald's expanded, the arches became a recognizable visual shorthand for the restaurant chain. In 1962, designer Jim Schindler combined the two arches into the familiar letter-like M used in the company's logo. The architectural structures and the later graphic mark are related, but they are not exactly the same thing.
A common mix-up is calling the symbol simply the “McDonald's M.” The established branding term is “Golden Arches,” and it is also used more broadly to refer to McDonald's worldwide identity.