You can pin important items in your conversations that you want to easily access later. When you mouse over comments in the chats, you will see a grey pin appear along the left hand side. If you click on the pin, it will turn yellow to show it as "pinned".
You can access the items you have pinned from the main navigation dropdown on the top right of the screen. Select "Pinned" and all of your pinned items will then appear on the right side of the page. You can easily unpin something by clicking on the pin again when you no longer wish it on this list.