Here's a brief overview:

Vinyl replacement windows are becoming more and more popular because they are usually more affordable than other types. The vinyl extrusions used for the sash and frame are hollow, but reinforced with internal braces that provide extra strength. Depending on the manufacturer, the vinyl will come in white only or a limited number of colors. The material is paintable. Vinyl won't rot, warp or be damaged by moisture or exposure to sunlight.

Fiberglass replacement windows are similar to vinyl units in appearance and construction. Fiberglass is slightly stronger than vinyl, and will not expand or contract as much in response to temperature changes, but it's also more expensive. Like vinyl, fiberglass is paintable and can't be damaged by mold, moisture or sunlight.

Aluminum replacement windows are more common in commercial than in residential applications. Aluminum conducts heat more effectively than wood, vinyl or fiberglass, so it's not good for energy efficiency unless thermal breaks are installed. This can make good-quality aluminum replacement windows more expensive than other types.

Wood replacement windows usually have their exterior surfaces protected with a thin cladding made from aluminum or vinyl, so they're often referred to as "aluminum-clad" or "vinyl-clad" windows. Since wood requires maintenance (painting or finishing) and can be damaged by moisture and UV exposure, these replacement windows are most likely to be used in historic houses or when the homeowner wants the look and feel of real wood.