Basically robosang is correct.
SKKCA-21 is a starter kit for KC21 Bluetooth module. If you take a look at the datasheet of KC21, it require connection to a host, normally is microcontroller or a computer via UART connection.
UART is the method/way for this Bluetooth to communicate with host, and that is the purpose of Bluetooth module. In most of cases, for example, we use SKKCA-21 is for connection to microcontroller because if I wanted to connect to computer, I will be using
USB Bluetooth Dongle. You can refer to
PR6A for simple example and get an idea on what can be done with SKKCA-21.
As for the programming language. As long as you can access to COM port for computer, you can develop program for it. Once the Bluetooth is connected, it become a wireless serial port. What ever a node send, it will automatically send to the other node and further transfer that to its host via UART.