HC-05 6 Pin Wireless Serial Bluetooth Module is a Bluetooth module for use with any microcontroller.  It uses the UART protocol to make it easy to send and receive data wirelessly. The HC-06 module is a slave only device.  This means that it can connect to most phones and computers with Bluetooth but it cannot connect to another slave-only device such as keyboards and other HC-06 modules.  To connect with other slave devices a master module would be necessary such as the HC-05 version which can do both master and slave.