Modern high-speed ports can carry data, video and power over one cable, so a laptop can connect to a dock that drives monitors, charges the machine and links peripherals through a single connection, replacing a tangle of separate cables.
This simplifies desks and makes it easy to arrive, plug in once and have a full workstation. The fastest connections also allow demanding uses like external graphics and quick storage. Capabilities vary between ports and cables that look alike, which can confuse, but the convenience of a true one-cable setup has made these connections a prized feature on laptops.