The option key is an often ignored key on the Apple keyboard. This is partly because it gets labelled many different things (Option, alt and ⌥), but also because people don’t realise quite how useful it can be.
For instance if you open any menu in an application and then hold down the option key you will see alternative menu options appear. It’s also useful when used in conjunction with multiple shortcuts. For instance if you append the option key to the ⌘ + W shortcut combination it becomes close all windows as opposed to just closing the current window.
Conduct a little exploration and see quite what the option key opens up for you in your favourite applications.
The Finder file menu (first image) and with the option key pressed (second image).