This one is quick and sweet. Try exploring pressing the Option Key along with different menu items to see the extra features available. For example, pressing Option before you press the Sound icon will allow you to choose different output devices to send your sound to. Pressing Option before you press the Apple Menu will allow you to check your System Information quickly.
And most importantly, clicking Option while you are selecting ‘Edit’ in Safari and Chrome will offer you such things as ‘Save As’ rather than ‘Save’.
There are lots of other features in places where the Option key will have an effect: experiment!