Apple makes things simple by working hard to figure out what you are likely to need most of the time. As you use your Mac more and more, there are times when the most likely thing isn't quite what you want —and with multiple ways to get from point A to B, Apple's got you covered there too.
All across macOS Sierra and in many other apps, the Option key unlocks handy features.
The Option key is regularly also labelled Alt and with most keyboards you've actually got two of them on the bottom row near the space bar. As you'll see, the way that you use this key isn't consistent, but in every case you're about to learn, pressing it gets you extra options.
For instance you can use this to skip the "Are you sure?" message when you want to empty the trash. You can close every window on your screen instead of schlepping around clicking on the red button on each individual one.
You can also troubleshoot wifi and Bluetooth problems or get finer audio controls.(The article continues...)