Here's some very good information on window maintenance from my favorite home inspector Jesse Longman with A-Pro:
There are many styles and types of windows. They may be single hung with one sash that goes up and down or double hung with two movable sashes. If the sash moves sideways it is called a slider. Hinged on the side and opening out is called a casement. Hinged at the top is an awning, and hinged on the bottom is a hopper.
There are a wide variety of glass options available today including:
Single Pane: Used almost exclusively until about 1950. Only one pane of glass is used in this type of window.
Double Pane: Double glazed windows have two panes of glass. The space in between is filled with a dried air or an inert gas such as “Argon”. If the seal in between the glass is lost, condensation may develop between the two panes and make the glass difficult to see through. Defective seals cannot be repaired. Discolored glass must be replaced.
Tempered Glass: Tempered glass is made three to five times stronger than regular glass by heating it and then cooling it very quickly. When the surface layer of tempered glass is broken, the entire pane shatters into small rectangular pieces.
Laminated Glass: A layer of plastic is sandwiched between two layers of glass to prevent broken pieces from being released if a pane is cracked or shattered.
Periodically inspect the exterior of the windows for physical damage or signs of water damage.
Check for broken, cracked, loose, or missing glass. Check double paned units for signs of seal failure (fogging between the glass).
Regularly check the windows for drafts and smooth operation. Clean & oil regularly. Check for peeling paint.