The main menu will change depending on what context you're in while interacting with your cloud.
For example, after you log in, you'll be directed to your default cloud dashboard. The context here is "cloud context", so you'll see a summary of all of the sites within this cloud.
The menu, as shown below, will show you options and settings that apply to the current cloud. The "Devices" menu option will show you ALL devices in your cloud, across all sites. The same goes for the "Clients" and "System Activity" menu options.
NOTE: Non-administrators may see fewer options than the standard user.
Next, if you dig deeper, and choose a Site from the "Choose a Site" drop down, you'll be directed to the site-level dashboard, which shows a status summary of the devices within that site.
The menu is also updated so that site-specific options are presented. The "Devices" menu option will now only show the devices within the current site.
Let's say you continue on and click on a device from the device list. You will then see a device-level menu. Again, the menu items on the device-level menu only apply to the currently selected device.
Finally, once at a lower level, you can easily navigate to the upper-level context menus by using the arrows at the top of the menu: