Immediately after Login you will be notified with a yellow bar at the top of top of the screen. If you are the first user after a long time of inactivity, the database has to be loaded on the web-server, and a progress message is shown in the upper right corner. Please wait until the progress is at 100%, and it will disappear.
Some more common elements are explained in the following figure
The connection trend shows the quality of your Internet connection. If it is a green circle your connection is fine, clicking the icon will open a window showing the connection trend over time. Clicking the question mark in this window will give performance parameters for the web server.