Paper clip trick??

Can anyone tell me what this is / how to do it?
Thanks

Something to do with codes?

short out contacts on OBD connector located under driver dash.

and what does this do??

and what does this do??
It allows you to read the diagnostic codes in the computer when the "check engine" light comes on. This way you can bypass a costly shop diagnosis. Almost any repair manual from a parts store will explain how to do it.