This adapter has an M1 male connector on one end and an HDMI female connector on the other end. In addition, it has "thumb screws" on the M1 connector that allow you to secure the adapter on the projector.
This adapter allows you to use an HDMI cable to connect to a projector that has an M1 female connector. Many projector manufacturers decided to use one "universal" M1 connector instead of having many types of connectors for the different video formats.