From the in-game description, a market is a place where food, water, essentials, etc are collected from warehouses, town centre, water tank, etc. But that is not all.
What Is Market For?
Storage + transfer station
A market has settings where you control what stores in this market, how many and where these materials will be taken from by logisticiens, and distribute to settlers. Give attractiveness at the same time, and it is a good building to fill up the space between residential and factory/farm field areas.
IMO, food station and water point are quiet useless. Market and kitchen can function as food station, and electric water pump can function as water point. No need to have specific logisticiens for food and water delivering.
The Market has evolved
Think of it as a mobile, ploppable Town Centre/Hall when you want to expand your settlement.
Once I have a few Markets placed and storing the necessities, I’d turn their storage off at the Town Hall.
Before we had Decorations (I think it is this game where it was added later, if not apologies it has been awhile), we didn’t have a way to counter the negative effects on Happiness from the dirty production buildings. So, the Food Station and Water Points were a stop gap placed in between Market and Industry; or to keep workers fed/watered without them having to travel back to their Homes.
You have to make sure your worker dont have to walk a long way to get food, water, resources (in some industry) and entertainment (pub). Market can provide first three, you can set market to fetch some resources such as wood so the worker can grab them from market directly without walking a long way.