For instance, what does it tell us about an era to know it made horrid iron harness devices with a bell to be worn by enslaved people as punishment (as if being enslaved weren't punishment enough)? What value did people in the 1940s place on radio, that they housed the ugly tubes and wires in mahogany cases called "cathedral style"?
If you write about historic eras or other worlds of the imagination, you have to think through these overarching, meta-level relationships between people and the objects in their environment in order to recreate the past or to create a compelling story world.
But how people relate to their belongings is significant on an individual level too. I'm perhaps more steeped in this aspect at the moment.
A character in my work-in-progress is someone who hoards aspirationally. He fills his home with things he thinks will enhance his image. But he's not wealthy enough to collect macho sports cars or hire marble sculptors to enshrine him in stone, so his collections are more modest but just as unable to satiate his underlying emotional need.
Next week I head south to help my mother purge belongings and pack for a move from independent to assisted living--going from six rooms, six closets to two rooms, two closets. It's not the physical work of packing I dread most, it's the emotional minefield I'll have to navigate as Mom contemplates parting with stuff she doesn't need but nonetheless can't imagine not having. Some deep ties will have to be severed so she has room to move in her new home.
We develop strong ties with objects over the course of a lifetime. Those ties in a sense can define our character. Perhaps it is a childhood toy that seems to hold all the magic of innocent, happy times (Rosebud in the film Citizen Kane comes to mind). Perhaps it's an inherited tool that confers familial blessing on an endeavor, like a pastry chef who relies on her great-grandma's rolling pin to create award-winning pastries. Perhaps it is a long-coveted object that once possessed gives one a sense of having "arrived" in the land of success, like a gold Rolex watch.
As you develop your story world, both large scale and small, consider the power of material culture to build and enhance your characterization.
What special objects in your life hold significance for you? Have you used significant objects in your writing to illuminate a culture or a person?