Question: Ubuntu has a feature where application windows can be set to be always on top of other windows. Is this possible in Mac?

Check out Afloat.

it will add many window management features to most Mac applications:

• Keep windows afloat (heh) on top of all others.
• Pin windows to the desktop (new!)
• Move windows from anywhere, not just the title bar.
• Turn a window into an “overlay” on your screen that doesn’t hinder your work.
• Show a window’s file in the Finder with nothing more than your keyboard.
• Resize windows from anywhere, not just the corner (new!), and more.