The Raspberry Pi 2 Model B has a Quad-core 900MHz Processor, 1GB RAM, 4x USB Ports, 40x GPIO Pins, microSD connector and full 1080p HDMI video support. It is the first edition of the Raspberry Pi that is built to support Windows 10 IoT. (This item posts for free)
The Raspberry Pi 3 Model B+ (Released March, 2018) has a quad-core 64-bit 1.4GHz Processor, 1GB Ram and onboard Dual-band 802.11ac wireless LAN and Bluetooth 4.2 (including BLE).
This edition allows for PXE network and USB mass-storage booting and has a Gigabit Ethernet Network Interface.
The Raspberry Pi Zero WH is the smallest Raspberry Pi. It has onboard WiFi and Bluetooth. It has a micro SD card slot, a mini HDMI port, two micro USB ports (one for power, one for USB), and 512MB of RAM, and is powered by a single-core 1 GHz processor.