The budswitch is a very handy redstone tool that is kind of a glitch that has played an important role in redstone. Budswitches use block updates to activate redstone. Althought there are many variations on the budswitch, in this tutorial I will be showing you one that is very commonly used.
The way to activate it is to update the block beside the black end on the sticky piston also, use the second redstone torch to activate your other redstone. Another way to activate it is just to update the block beside the piston which includes any way you change a block. ex: opening or closing a fence gate walking over tripwire. Those sorts of things. Also there are redstone lamp budswitches.