Progress window is used for various winIDEA processes to track their execution. It also shows information in progress bars.
To open the Progress Window go to View / Workspace / Progress.
Markers on the right side of the window are indication errors. If a task fails, the Progress window title is marked red.
Progress dialog with task bar pops out, when executing a task. Opening Progress window on a change can be disabled in Tools / Options / Environment / IDE section / Open progress view on change.