Resist 1 all such as is profiled by
Rimefire Plate +2 prevent normal / untyped damage, such as is done by an axe or arrow?
This is clarified, albeit obliquely in the official FAQ.
Unfortunately, the rules are unclear about what "Resist All" means.
At the very least though we can assume that Resist All reduces damage from all attack types, including normal and untyped damage.
What is less clear: Does "Resist All" mean "resist everything" or "resist all damage" or "resist all damage types"?
If you believe "Resist All" means "Resist All Damage Types" (#3), then you must decide whether "all damage types" includes untyped/normal damage. The rules do not specify that untyped damage is really a type of damage. Each DM will have to decide if this is the case. If untyped is a damage type, then "Resist All Damage Types" should reduce untyped damage; otherwise, it should not. The rules (and logic) are stacked against untyped damage being a type of damage, however.
Some people believe that the Adamantine Weapon magic item provides evidence that Resist All applies to untyped damage. If this is the case, then the "Resist All Damage Types" interpretation probably isn't true. The item description reads:
Also, if your "Resist All" is described as Variable Resistance, then the rules will be different. Variable resistance reduces one type of damage at a time until changed, and activating it is usually a free action that can be done a certain number of times per encounter.
If "Resist All" means "Resist All Damage Types," then it probably doesn't reduce normal / untyped damage, because that's not a type. More likely, "Resist All" means "Resist Everything" or "Resist All Damage." This means that it reduces the damage and may or may not include generic resistance against all other effects.
I would say that "rules as intended" is that you reduce all damage you suffer by 1.
Which would be "Resist Everything" in Adam Dray's answer.