A storage jar is the thing that keeps flour, sugar, rice, pasta, coffee, tea, or whatever you cook with most out in the open without turning your counter into a mess. It takes food out of bags and boxes that rip, spill, and attract pantry moths, and it puts it somewhere you can see what you have and how much is left. That's the whole job. It sounds small until you're standing there wondering if you already bought rice.
If you're starting from nothing, get two or three jars in the same size and shape before you get a matched set of fifteen. You want one for flour, one for sugar, one for whatever grain you cook most, and you want them to actually hold a full bag of each so you're not left with a sad half cup in the original packet shoved behind them. Glass over anything else for your first jars, because you can see the contents and the level without opening the lid, which matters more than it sounds like it should when you're trying to remember if you're nearly out of oats.
The difference between a jar that earns its spot and one that ends up in the donation box comes down to the seal and the glass itself. A good one has a lid that clamps down with a rubber gasket or clicks into a groove, and it holds that seal for years without the rubber perishing or the clip snapping off in your hand. Cheap ones have lids that look right in the shop and then warp within a month so the seal goes soft and you get stale crackers and weevils in your flour. Look at the glass too, thicker glass doesn't yellow or scratch the way thin glass does, and a wide neck matters more than people expect, since a narrow one means you're pouring and fighting a funnel every single time.
These suit a kitchen with some counter or shelf space to spare, and they come into their own in autumn and winter when you're baking more and want the ingredients close and visible rather than buried in a cupboard. They're less useful in a kitchen with no surface space at all, where every jar becomes one more thing to shuffle around, and they're a poor match for anything you use in tiny quantities, like spices, where a jar that size just wastes freshness and shelf room.
Keep the lids away from the dishwasher's heat cycle if they have rubber seals, since that's what breaks them down first.