For years I thought place mats were a thing other people's mothers used, something that showed up at a dinner party and made the table look like it was trying too hard. Then I spent a winter wiping water rings off a secondhand table and realized a tablecloth is a hassle and bare wood is a liability, and place mats are just the quiet fix sitting in between.
They work in almost any room where people actually eat, which in a lot of houses is not the dining room at all, it's the kitchen table that does breakfast, homework and dinner on rotation. Woven or rattan ones feel right in a kitchen that gets a lot of daylight and a lot of use, something you can wipe down and not think about. Fabric or linen mats suit a table that's trying to look a bit more done, the one you pull out for people you actually invited over. Cork and bamboo handle heat without flinching, which matters more than people admit until someone sets down a pan straight off the stove. Come fall, a thicker woven or felt mat makes a plain table feel like it's dressed for the season without you doing anything else to the room.
Sizing is where people either get this right in five minutes or overthink it for a week, and I've done both. Measure your table setting the way you'd actually sit at it, plate, glass, cutlery, and make sure the mat gives you a couple of inches of breathing room on every side, not a tight fit the plate hangs off. Rectangular mats suit most rectangular tables without argument, but round tables need a slightly smaller mat than you'd guess, otherwise the edges overlap and it looks like a crowded elevator. The mistake is buying one size for a six person table and assuming it works the same at a table for four, it doesn't, the proportions shift more than you'd think looking at a product photo.
If you own none, start with a set of four in a plain woven neutral, something that works under everyday plates and under better ones, so you're not buying twice when the first set turns out to only suit one mood. Cloth is nicer to the touch and easier to launder than people expect, which makes it the one upgrade worth doing before anything fancier.
The good ones have a little weight to them, enough that they don't slide every time a kid reaches for the butter.