The Everspring HAC01 In-Wall Remote is a Z-Wave transmitter that can control other Z-Wave devices by association.
The In-Wall Remote can control Z-Wave ON/Off switches (relays) and dimmers and can act as a Z-Wave repeater helping to strengthen the Z-Wave mesh network.
It can also be connected to a wired switch or binary sensor enabling them to send Z commands and control other Z-Wave devices. For instance you could wire the HAC01 to a wall switch and associate it with a Z-Wave dimmer. You will then be able to control the Z-Wave dimmer wirelessly from the HAC01's wall switch.
Note: The HAC01 requires a 3-wire system (including neutral), please check your installation before purchasing. More information is available in Application Note 23 - Understanding 2-wire and 3-wire Lighting Systems.