Energy use intensity and water use intensity are ways to measure normalized consumption of a resource.
Typically this is expressed on a “per square foot” or “per square meter” basis. So, for energy it could be kWh/sqft or GJ / sqm. For water gal/sqft or L/sqm.
It is possible that “use intensity” can also be measured against other normalizing factors such as “widgets produced”, “room nights”, “food covers”, “sales revenues”.
Energy and water use is often dependent on some other factors in a building or a business process. If you have a need to compage use over time or across facilities, “use intensity” is one way to accomplish that!