Ha,ha thats an easy one. It it doing exactly what it is supposed to do. If you would like to stop it and other apps from doing this go to System Preferences > Dock and untick "Minimise Applications into Application Icon". This way you can have more than one instance of the same app open at the same time like MS Word, you can have 3,4,5 pages minimised on the dock.
The minimised pages/apps will now be to the right of the Dock divider down near Trash and your Downloads folder, left click once to maximise.
Ha,ha thats an easy one. It it doing exactly what it is supposed to do. If you would like to stop it and other apps from doing this go to System Preferences > Dock and untick "Minimise Applications into Application Icon". This way you can have more than one instance of the same app open at the same time like MS Word, you can have 3,4,5 pages minimised on the dock.
The minimised pages/apps will now be to the right of the Dock divider down near Trash and your Downloads folder, left click once to maximise.
Activity Monitor has the same behavior.Its the only app I have that exhibits that behavior. Safari minimizes by trash and downloads like you describe but click its original icon maximizes it again alone with all my other programs. Only notes doesn't reopen when clicking its icon.