A blouse is the top that makes the rest of an outfit look deliberate. Softer than a shirt, with more shape through the body and usually something happening at the sleeve or the neckline. It is what you put on when jeans need to read as a choice rather than a default.
▾ What is the difference between a blouse and a shirt?
A shirt is built on a collar, a button placket and a straight cut. A blouse borrows what it wants from that and drops the rest, so you get ties, ruffles, puff sleeves, wrap fronts and necklines that a shirt would never carry. The practical difference is where each one lands: a shirt reads as workwear or as a layer, and a blouse reads as the top itself. If you are deciding between them, ask whether it is going over something or being looked at.
▾ When is a blouse the right call?
Anywhere you want the outfit to look thought about without looking formal. Dinner, a birthday, meeting someone's parents, the day that starts at work and does not end there. It sits over jeans as easily as over a skirt, and it is the easiest way to make a plain bottom half look finished.
Blouses sit in Tops. For a harder edge on the same night out, take a corset top instead.