An Impact Vest is designed primarily for protection and freedom of movement rather than buoyancy. They do, however, offer up to 50N of buoyancy in some cases. Impact Vests are intended for use during high-speed watersports by intermediate to advanced riders where potential injury could occur from coming into contact with the water (or obstacles / equipment) hard. Impact Vests are tight fitting so that they stay put during a fall and many have no openings so are pulled over the head rather than zipped or buckled up. Impact vests are generally thinner than Buoyancy Aids and often have visible panels for added protection in critical areas of the torso and spine.
A Buoyancy Aid is designed to make life easier if you are taking part in any water sport that involves you actually being in the water a reasonable amount. A Buoyancy Aid will assist you greatly in terms of being able to tread water, but generally speaking you still need to be able to swim in order to stay afloat. A Good Buoyancy Aid will also provide a certain amount of insulation on cold days and most will provide varying amounts of impact protection depending on their design and the materials used. The accepted standard for a Buoyancy Aid is that is provides 50N of floatation and that it is ISO-approved. Buoyancy Aids are worn like a jacket and fasten at the front or side with either snap buckles or zips (or both). As with most things, you get what you pay for and we recommend that you should always spend as much as you can comfortably afford. The more expensive PFD's are made from higher quality materials, are more comfortable, and have more adjustments / features.
A Life Jacket differs from a Buoyancy Aid in that it is designed primarily to keep you afloat, even if you can't swim, and to rotate you onto your back if you are unconscious so that your head is held above water and you can breathe. For this reason, Life Jackets tend to be bulky and have a pronounced head / neck support plus straps to ensure that the jacket does not come off if the user is thrown into the water at speed. Wearing a Life Jacket for most recreational water sports is impractical (and can be quite uncomfortable), but using them on a boat or for kayaking is perfect, and if you want to tow younger kids in towable inflatables then we also recommend Life Jackets for this purpose too.