It's a UniCord port, Apple's proprietary port to save space. By 2026 it will be the only port on new Macs.
The press release:
Apple UniCord
Designed as the ultimate unifying connector, UniCord could serve as Apple's next-gen cable standard, integrating data transfer, power, and display into one sleek cable. With faster data rates, higher power delivery, and cross-device compatibility, UniCord would embody Apple's minimalistic philosophy—one cord for everything, from iPhones to Macs, AirPods to iPads.
Marketing line: "UniCord. One connection, endless possibilities."