It does +Jonathan Seyghal
, they are called labels and are probably located in your left pane below your various email boxes (inbox, important, sent mail, etc for example) and above the Chat section of the pane. When you hover your mouse over it an option for "More" should appear which should reveal options to create new and manage existing labels. Once made, just drag the label you want onto any email and it will forever carry that label. When you click on that label in the left pane, all emails with that label will be listed.