While the above answer is true, be careful! There is another meaning for "out-of-the-box" which is more commonly used - and which carries a nearly OPPOSITE meaning. The idiom "out of the box" (or "out-of-the-box") most often means "creative, unusual, NOT the same as others' ideas". It can be used as an adjective or an adverb. For instance: "Jerry thinks out of the box. He is always coming up with new ideas for the company." "Jerry is an out-of-the-box kind of guy. You never know what he will do next!" "We are looking for people who think outside the box. We want innovative leaders, not followers." Notice, in the last example there, that it can be written "outside the box" OR "outside of the box".

'out-of-the-box' is an instant solution. Something that works at once. Ready to be used quickly, without any modifications. It doesn't have to be a real item. Techniques and behavioural patterns are also possible. A standard answer, for example. Some computers are said to be ready for use when you unpack them. (I don't think so. My computers need about one week of configuration before I think they are safe and ready to work with.)

Erik's awnser is perfect!!