What does the word "boot" mean?
Versalog already told the core of the thing. Most prop aircraft which are approved for flights into known icing conditions have such boots to remove the ice from the wings leading edge.
Those boots are either inflated manually whenever you need them (by the press of a button of course), at regular intervals or automatically whenever ice is detected.

Check this picture, the black thing is the boot on a Dash 8's wing:


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