Keyboard Shortcuts are real time savers, they are pretty hand and help to keep you productive to perform time consuming tasks quickly. If you are a Gmail user, you can make use of keyboard shortcuts to quickly compose emails, iterate between messages, open current messages, archive messages, star them and more.
You can find a extensive list of Gmail keyboard shortcuts at the help page for keyboard shortcuts, if you would like to print the keyboard shortcuts, you can use the printer friendly keyboard shortcuts.
You will have to enable the keyboard shortcuts in your Gmail account before you can use them, to do that go to Settings > General and turn keyboard shortcuts on.
Looking for more tips for Gmail, checkout the Gmail Tips section to get handy tips and tools for Gmail.