A capability is something a person or a thing is able to do. It's hard to find a cell phone that doesn't include other capabilities, like taking pictures or storing MP3s.
Inside the word capability is the word ability. Note the fine distinction between them. If you have an ability, it means you know how to do something. If you have a capability, it means you have the power to do something. Buying uranium gives a country the capability of making nuclear weapons, but first they need scientists with the ability to do the work.