TTS, or True To Size, is a term used to describe the fit of a sneaker. It means that the sneaker will fit as expected in relation to the size that you typically wear. In other words, if you normally wear a size 9 in shoes, a TTS sneaker in size 9 should fit you comfortably without the need for sizing up or down. It's important to note that TTS can vary between different brands and models, so it's always a good idea to check reviews or try on the sneaker before purchasing.