What do you call the sets of window bars that are used to protect the window and are opened to the outside?
Window grille:
A grille is a framework of metal bars or wire which is placed in front of a window or a piece of machinery, in order to protect it or to protect people.
(Collins)
They’re window security bars. The pictured ones are belly-style. They must be quick-open (without a key) to enable exit to the ground or a fire escape.
As pictured, they protect against entry frm the outside. Also called burglar bars.