The Advanced options enables expert views and configuration options in the client. Usually users just need the simple mode (default) to perform the most basic actions, however advanced users might want to see more details and configure the client and folders more deeply to make it work like they want.
Enabling the Advanced Mode
To enable the Expert Mode:
Click on Preferences in the main window.
Mark the Show advanced options checkbox.
Click on OK.
After enabling the Advanced Mode the client will ask for a restart. Please click on Restart to confirm that.