They say that power corrupts, but absolute power is really cool! So true.
But using the right extension cord for the right power is really smart. All to often, people will use a power tool with an extension cord that is either too small in gauge or too long in length for a particular tool. Using the wrong cord can result in frying the motor in the tool, frying the extension cord, burning down your house, plagues of frogs and locust, etc.
Here's what you want to do first. On your power tool, there should be a spec plate somewhere on it that tells you how many amps it draws. If the amps are below 7 amps, you can comfortably use a 16 gauge extension cord. If the amp rating is closer to 10 amps, I would recommend a 14 gauge cord. And anything near or above 15 amps, you most definitely should be using a 12 gauge extension cord.
Remember too, the longer length of the cord puts more strain on the load and can result in damage too, even if the gauge of the cord is right for the amp load of the tool