From what I cobbled together from various sites, it served like a steeple on early churches, with the same origin- a way to recognize the center of worship in the town. That is the ‘light’ it refers to. Like Christian churches used bells to call someone to church, Muslims had a call to prayer from the top of it so everyone could hear.
Remember, the origins of this were during a time when timekeeping instruments were rare so something like a regular call to prayer served as a good timekeeping device as well.
Not in the Catholic dictionary. Not in the New Advent Catholic encyclopedia. Tells you something.
From what I could glean without clicking on anything it is a steeple sort of thing with a balcony on which someone can stand and call people to prayer.
*Why not just ring the bells like Catholics do?” My question — LOL!