It can do whatever you want it to do. The examples in the article were:

• whenever any USB drive is removed, trigger xscreensaver to lock the screen:

> ACTION=="remove", SUBSYSTEM=="usb", RUN+="DISPLAY=:0 xscreensaver-command -lock"

• whenever a specific USB drive is removed, shut down the computer:

> ACTION=="remove", SUBSYSTEM=="usb", ENV{ID_MODEL}=="Micromax_A74", RUN+="shutdown -h now"