Many laptops and other items of electronic equipment use USB C connectors. It is possible to obtain USB C to HDMI cables and thereby conenct a USB C connector to another equipment that uses HDMI.
The HDMI alternate mode lets a user connect the reversible USB-C connector with the HDMI source devices (mobile, tablet, laptop). This cable connects to video display/sink devices using any of the native HDMI connectors. This is an HDMI cable, in this case a USB-C to HDMI cable.