The answers to questions like this can be found in the spreadsheets in folder (Program Files) > Dragon Age > tools > Source > 2DA.
itemprps.xls is a list of all the Item Properties. The IPType column identifies which ones are On Hit etc.
The Effect column identifies a corresponding effect number in effects.xls. Often, several Item Properties are implemented as the same Effect.
With a little patience, you can generally figure out exactly what an Item Property does. The Int and Float columns are parameters to the Effect.
For example, Increase Strength uses EFFECT_TYPE_MODIFY_PROPERTY with parameters (1, 0, 1.0, 0.0). The corresponding effect function is EffectModifyProperty (that name doesn't appear in effects.xls, but the naming convention is systematic). The help information for that function (in the toolset or the wiki) tells us this means "increase property number 1 by 1.0". Properties are defined in properties.xls, where we see property number 1 is Strength.