A Feature is about Your Product
Features talk about your product. For example, a feature of a car might be that it's blue and has a v6 engine. A feature of a laptop is that it has 1Ghz CPU and 512Mb of RAM.
Features don't sell products, they just talk about the finer details and most people don't care about features unless they're experienced in buying the specific type of product you're trying to sell.
A Benefit is about Your Client
Benefits talk about what the product will do for you and how it will save you money or make you richer.
For example, a v6 engine sounds powerful and goes fast. "Sounds powerful and goes fast" are your benefits and they make people really understand why they should by your product.
As another example, a blue car will spend less time in the car-wash than a white car and, if it's a snazzy metallic blue, it will make you look cool and fresh.
Benefits tell people what results they can get from using your products. They explain how people will feel when using your product or the time they'll save from buying from you instead of buying from your competitors.
How to turn Features into Benefits
Before: This car comes in metallic blue"
After: "This car comes in metallic blue so you can impress your friends and minimise 'car-wash' Saturdays!"
Before: "The car sports v6 engine"
After: "The car's v6 engine will have you whizzing around corners and roaring down straight-ways."
You can do this with just about ANY feature and I can guarantee you better results just from focusing more time on your client and less on your product.