A peplum dress is the one that makes a straight-up-and-down shape look like it has a waist, and if you've got a bit more going on through the middle and not much on top, it does the opposite trick, nipping in and skimming out at exactly the point you want attention to land. I tried one on expecting it to look fussy and it did the actual job it promised, which surprised me more than it should have.
It's not a dress for every occasion though, whatever the label says. If you're already curvy through the hip, a peplum can double you up there, adding a flounce exactly where you don't need extra volume, so it's worth trying before you buy rather than trusting the hanger. It's also a dress that reads quite formal and a bit fitted, so anything outdoorsy, anything with walking involved, anything where you'll be sat on a low chair for three hours, forget it, the peplum rides and creases and you'll spend the night tugging it back into place. As for wear and tear, the structure lives in that flared bit at the waist, usually a stiffer lining or interfacing, and that's the part that gives first. After a few washes on a bad cycle mine went soft and the peplum stopped sitting out properly, just folded down like a sad frill instead of standing proud. Hand wash it or use a delicates bag on a cold cycle, and hang it rather than fold it in a drawer, because creases through that seam are stubborn and an iron on the wrong setting will flatten the shape for good. Keep it in a suit bag or similar if it's travelling, a peplum thrown loose into a case comes out looking deflated.
Plain, solid colours work best because the shape is already doing a lot of visual work, so a busy print on top of a flared peplum can end up looking like two dresses had an argument. Navy, a deep berry, black, a solid jewel tone, these all let the cut be the interesting bit. Avoid pairing it with anything else structured or voluminous, a stiff jacket with its own strong shoulder, a full skirt layered underneath, a wide statement belt on top, because the peplum needs to be the one shape doing the talking, not competing with another one. Reach for it when you want a dress that does the smart, put together thing without you having to think about styling it much, a daytime event with some standing around, an evening do where you want structure but not a slinky fit. It's not for comfort days. It's for the days you want to look like you tried, because you clearly have.