I cringed when the subject of wards came up.
My two cents, and i'll try to be brief but clear.
A "ward" is any kind of Rego spell that is protective in nature and measures its range from the magus to the thing protected and not to the thing protected against.
Some wards affect how a thing acts around the warded subject. For example, Cloak of Duck's Feathers (ReAq5) is a ward because its range is Touch (i.e. the object/person touched, which is then warded against water as described in the spell.) Clearly the caster is not "touching" each bit of water that comes into contact with the object for until the next sunrise/sunset. It makes liquid roll off the object without making it wet. As I read it, the subject is touched by the water, it just rolls of him. Otherwise the base would have to be higher (Working backwards from HoH: S, the base to ward against natural liquids is 5). Similarly, the ReAn 5 ward I originally posted is a "ward" in this sense that doesn't prevent touch.
Other wards are the "true wards" that prohibit the warded Form from touching the warded object at all. Ward Against Heat and Flames falls into this category as does the ReAn 15 spell I posted earlier. Also in this category are the well known circular wards against foos, with their added benefit of prohibiting the warded Form from affecting the circle, or across it.
Finally "Warding" is a supernatural ability of the Columbae which has its own set of caveats.
For the record, I subscribe to the "wards have to penetrate" school, although Form specific wards (i.e. ReAu Ward against Fairies of the Air vs. ReVi Ward against Fairies) get to double the usual penetration from the casting roll. E.g. when casting a Level 15 ReAu Ward against Fairies of the Air, the casting score ends up at 20. Normally this would give a penetration total of 5. Since the ward is Form specific that is doubled to 10. Had the maga used a generic Fairy Ward (ReVi 15) the penetration would have been only 5. If you incorporate an arcane connection into the ward spell you can boost penetration normally, however the spell then only wards against the specific individual that donated the AC.