It looks much bigger than just sheds to me. Plus it doesn't look like the type of community garden where a lot of vegetables are grown, more like leisure garden... basic gardens that go with a house.

It is called "Kolonihaveområde" which could be translated as "small garden" or "family garden". The pieces of land are not bigger than 400m² the houses must not be bigger than 50m², and it is not permitted to live in theses houses the entire year. The owners can live there only from April to October. Similar concepts exist in other countries like "Kleingarten" in German speaking countries, which literally means "small garden". It's something like allotment gardens in the UK, but the land is mainly used for recreational purposes and not so much for gardening.

No. Look at the close ups. Half the plot or more it taken up by houses that are more than ample for people to live in. These are not sheds, or simple shelters. They aren't mansions, but they are full sized houses by any standard, and luxury to some.

From the horse's mouth: https://www.quora.com/Urban-and-Regional-Planning-How-do-the-residents-of-Br%C3%B8ndby-Denmark-find-living-in-allotments-arranged-in-a-circle

Because most of the answers are from people in US (I think?)

Once you've had a garage, you can't live without one.

I was thinking about winter, Denmark has snow! Quite a few of the houses are more than just summer day-houses, so your car needs shelter. I'm from S. Africa btw.

Have you ever had to clear two feet worth of snow off of your car? Once you do, then you have to clear all that cleared snow off of your driveway, so you have to move it twice. And then, scraping ice off of a car in the morning when it's -15F is never fun. (I don't know if it gets quite that cold in Denmark, but it does snow there, I think.)