Characterised are the Impacts expressed as mid-point indicators such as GWP in kgCO2e.
For example: “This building emits 20,000kgCO2e over it’s life“.
Normalised are the Impacts expressed as a proportion of a common reference level. Usually the reference level is the per person impacts for a region or the globe of the indicator. This starts to give users an appreciation for the relative importance of the different indicators.
For example: “This building emits 1 average Australian’s annual GWP emissions over its life and emits 0.01 average Australian’s annual ODP over it’s life“.
Normalised and Weighted Impacts are the impacts expressed as a proportion of the common reference and then weighted. Generally it’s meant to account for the actual “damage” of the emission as well. By normalising and weighting you can come up with a “single score” for all indicators. You use Normalisation and Weighting to work out if an increase in one indicator, and decrease in another is a Net positive or net negative.
For example: “This building has an EcoPoint score of 0.51 representing the total relative damage of all indicators“.
Longer and more technical definitions found in the ILCD Handbook: General guide for Life Cycle Assessment – Detailed guidance. See section 6.7.6 page 113.
If you’re conducting the study for ISCA rating, you’ll want to use the last option: ‘Normalised & Weighted Impact Values (ISCA EnviroPoints v2.0 (Normalised))’