There are four types of auxiliary cameras available:
WiFi auxiliary cameras pair to the dashcam through WiFi, and do not need hardwiring to a router. If the auxiliary camera is going to be mounted near the dashcam, use the WiFi option. This eases installation.
Wired auxiliary cameras are hardwired to a router, which in turn should be paired to the dashcam. If the auxiliary camera is going to be mounted farther from the dashcam, or with a lot of metal in between, use the wired option. This increases reliability.
Side cameras come with hose clamps and a silicone pad. They are mounted on the mirrors of the vehicle.