Missoula Public Library now offers diagnostic tools to assist you in understanding your automobile!
There are two different kinds of devices. Two items (blue and green) are Bluetooth devices. These are used by plugging them into your automobile and using a Bluetooth device to read information from them. There are many apps that can be downloaded to smartphones and notebooks to read these devices. These two items are very similar, but blue is for generally older vehicles, and green is for newer vehicles.
The other two items (Red and Yellow), are devices used to check and change codes from the automobile. You just have to plug them into your car and they will display a code describing why your engine light has come on. Red is a fancy one, it will display the code number and the text of the code. Yellow is a bare bones device. It just displays the code (you would have to Google the code to find out what it means).
Each bag contains multiple components. A list of all components is included with each bag.
If you find this fascinating and wish to learn more, look up “on-board diagnostics” at Wikipedia.