Yes, you are correct. It's an interface protocol that is used in lighting, to control intensity/on/off and essentially dimming.
I'll be honest, in more than a decade of the US market, I have not knowingly come across a DALI interfaced lighting unit. This standard seems to be more prevalent internationally than in the US.
You may however, use this with any Dali interfaced ballast/lighting system if you want, maybe you have some lighting that is not reef specific, that speaks this.
I.E. About a decade ago I used an Aquarium controller that spoke x10 - and I used x10 modules in my home, so I controlled several items in my home from said aquarium controller. Specifically I had a 220v-high amp x10 switch that I used to turn y water heater on/off for when I wasn't home.