In most cases, sweat-proof and waterproof headphones are described as the same thing in product listings, but the truth is they are not. Some listings reference water resistance, as opposed to waterproofing, to avoid confusion, while others use the more popular term.  The best way to tell the resistance level of a piece of equipment or device is to look at the Ingress Protection rating. Ratings of IPX4 and IPX5 can withstand some moisture contact, like sweat or rain, but they are not protected from water immersion or pressurized jets. If you want to be able to submerge your devices, or use them while swimming, the protection rating must be IPX7 or higher.