Instead of folders, Gmail uses labels to organize your email. To view all messages with a specific label, click the label name on the sidebar. You can also enter the name of the label in the search box. To create a new label, click the More shortcut in the sidebar, and click the Create new label shortcut. Enter the label name, and click the Create button. You can nest labels under other labels, and apply multiple labels to a message.
If you want to label a message, check the box next to the message you want to label. Click the Labels button on the toolbar, and check the box next to the label you want to apply. Then click the Apply button and your message will be labeled.
If you need to determine where labels are displayed, click the Settings button on the toolbar. Select Settings, and click on the Labels tab. Click the show, hide, mark as unread, remove, or edit shortcuts in the Show in label list, Show in message list, and Actions columns.