We used to buy light bulbs based on their wattage, but a watt is a unit of consumption rather than of output. For example, a heater using 1000w an hour still doesn’t make a good light! We buy most other things based on what we are getting, not what they use. Technical advances have made bulbs more energy efficient, so using watts as a guide to brightness is no longer so helpful.
Lumens are a measure of the total amount of visible light (to the human eye) from a lamp or light source. They take the confusion out of choosing by showing how much light you can expect from a bulb, with a higher lumen value showing there will be more visible light. Packaging might also show a “useful lumens” rating. This is usually lower and is more relevant to a spotlight where it only counts the light focussed forwards.
So how do you use the system? As a rule of thumb, if you used to have a 60w incandescent bulb, replace it with one giving about 800-850 lumens. The most energy efficient bulbs are LED, which can produce the same amount of light for about a fifth of the energy, and last much longer. Norvetts use good quality LED lamps and can supply and install them for you.