For the average person, the multitude of glazing types available can be confusing and disconcerting.
Facing options like single glass, reflective, double, double low E, double low E low transmittance, spectrally selective toned, double low E argon filled, double toned, comfort plus, and single clear low E not to mention the number of framing options can require careful consideration.

A mixture of glazing types can be installed for differing performance requirements depending upon the location of the windows in your home.
For example in Melbourne you may decide to fit windows facing north with glass having a high solar heat gain factor (SHGC) to make the most of the winter sun (with screening for summer) and to windows facing east receiving low summer sun penetrating below pergolas, a glazing with a low SHGC to help keep the heat out.
In all cases the lower the U-value of the window assembly the better.

Confused?
The higher the SHGC  the more the radiant solar heat is let in. The lower, the more is reflected back off the glass.
The lower the U value the lower the amount of heat that is transferred from one side of the glass to the other. In cold climates we want to keep the heat inside the home. In hot climates we don't want the hotter outside air conducting to inside.

Another terminology that you will possibly come across is Low-E.
Low-emission glass is a clear glass which has a thin virtually invisible coating of metal oxide.  Depending upon the application this can allow the sun's heat and light to pass through the glass into the building, at the same time it blocks heat from leaving the room, reducing heat loss considerably.
Different types of Low-E coatings have been designed to allow for high solar gain, moderate solar gain, or low solar gain.

As an aside, there is a product not widely known that has been around for quite a while.

Self-cleaning glass is an ordinary float glass with a special photocatalytic coating.
It is made by chemically bonding and integrating a microscopically-thin surface layer to the exterior surface of clear glass. The coating reacts to the sun's ultraviolet rays to gradually and continuously break down organic dirt through what is called a photocatalytic effect -  the active integrated coating on the outside of the glass absorbs the sun's ultraviolet rays. This causes a reaction on the surface which breaks down dirt and loosens it from the glass.
This type of glass also has hydrophilic properties, meaning that rain flows down the pane as a sheet, washing away the dirt instead of, as with normal glasses, leaving the dirt behind. As a result of these two effects, the special self-cleaning coating keeps the glass cleaner for a longer period than with normal glass in applications where it is exposed to the rain.