The Thunderbolt 3 to Thunderbolt 2 adapter lets you connect Thunderbolt and Thunderbolt 2 devices with external hard drives and Thunderbolt displays 

The thunderbolt 2 port can connect the hard disk and Apple displays (It cannot connect the mini DisplayPort device and can not work for mini-DP mode)

Note: the adapter only can work for 2016 Macbook Pro Thunderbolt 3 USB-C 40Gbps port. It cannot work for the USB-C 5Gbps/10Gbps Macbook.