Zero W is the Smallest in Raspberry pi Family with inbuilt WiFi and Bluetooth.
It provides great connectivity with 2 Micro USB Ports(1 port for Power and other for USB Connectivity), 1 mini HDMI Port and 1 Micro SD Car Slot and has 512MB of RAM.
It has same Processor as Pi 1 i.e Broadcom BCM2835 processor with clock speed is 1 GHz ..
 
Specifications:-
Broadcom BCM2835 1GHz processor
512MB RAM 
Mini HDMI and USB On-The-Go port 
Micro USB power 
HAT-compatible 40-pin header 
Composite video and reset headers 
CSI camera connector 
802.11b/g/n Wireless LAN 
Bluetooth 4.1 
Bluetooth Low Energy (BLE)