Water-Resistant: The computer peripheral can be wiped clean with a damp or wet cloth. It should not be damaged by sweating (often important for earphone users while exercising), and a splash of water likely won't damage it. It's not meant to take a run through a dishwasher.
Washable: The computer peripheral can be rinsed beneath the faucet and can often withstand a mild detergent. It may or may not be able to withstand a run through the dishwasher.
Waterproof: The computer peripheral can be submerged completely in water. The depth and length of time it can be submerged will vary. It can usually withstand a run through the dishwasher. It is important to note that while a peripheral may be signaled as being waterproof, its connector mostly likely will not be.