So imagine you have a big, long piece of paper that's divided into a bunch of little sections, kind of like a checkerboard. Each little section is called a column.
Now imagine there's a grown-up magazine or newspaper that gets printed on this big, long piece of paper. They use those columns to write different stories or articles.
For example, one column might have a story about a cat who likes to wear hats, another column might have a recipe for making a yummy dessert, and another might have news about what's happening in the world.
So when you read a magazine or newspaper, you'll often see it split up into different sections, and each section will have a bunch of those columns with different stories or articles in them. And that's what people mean when they talk about a "column" in a periodical - it's just one of those little sections of the paper that has some writing in it!