JBtek4 Channel DC 5V Relay Module for Arduino Raspberry Pi DSP AVR PIC ARM

How is this compatible with raspberry pi if it is 5v ttl? can i connect it to a raspberry pi and what voltage level activate it?

What is the third screw terminal for? i know one is gnd in and the other is gnd to accessory, but the control pins are on the other side.

Can the arduino/rpi drive this directly or are external drivers required?

Is diode stuff embed? do i need to hook it with external diode and pnp ect.?