If you use Gmail and don’t use labels, you must start immediately. Labels are a way of organizing your emails so you can quickly find what you’re looking for. For example, you may have labels for Trips, Receipts, Invites, Coupons, etc. And unlike folders (in most other mail clients), you can use multiple labels per email.
To label an email, open the message and click on the label icon (next to More, it looks like a tag). Choose an existing label, or type in a new one. Your labels will appear in the left column, and if you click on one you’ll see all the messages with that label.
Labels appear next to the subject of your emails in your inbox. If you want to change the color of your labels, click on the color box next to the labels in the left column and choose a different color.