Labels are Gmail's way to stay organized with your emails. You can create labels that store your emails. Labels work a little bit different than folders because an email can have multiple labels at once. Add as many labels as you want to an email and even give that label a color to help it POP it search results.
Give messages one or more descriptive labels, such as Project X.
Check the box next to one or more email messages.
At the top, click Labels .
Choose one of the following:
To make new labels, click Create new. Type the name of your label and click Create.
To select an existing label, click it in the list.
In the left sidebar, click a label to see messages with that label. Click More : Label color to change its color.
Label emails from your boss with a "Boss" label. You can use Gmail filters to automate labels from specific senders to come pre-labeled in your Inbox.
Labels emails from your least favorite project as PROJECT DOOM.
Label emails you have to follow up on with a "Follow Up" label and emails your waiting on feedback from as "Waiting."