The layer panel gives you an overview of all the items that are on your page and the order in which they are stacked. You can drag elements or groups up and down to change the order. You can also double click elements to change the name.
At the top of the panel there are options to use. Group, ungroup, duplicate and delete.
You can see an eye icon and a lock icon. The eye icon changes the visibility and the lock icon locks the element or group.