Ideas are what we think about, the output of mental activity. They are any object apprehended, inferred, perceived, conceived, or randomly thought of, within the mind. In a way the accumulation and moderation of our good ideas have helped form the backbone of civil society.
Some people think ideas are memetic, or they need protecting, while others think ideas are for sharing. Some people believe ideas are a form of unique information which requires effort to take the form of intellectual property that should be protected by copyright, trademark and patent law.
When ideas are acted upon and flourish, they often turn into visions, models or philosophies. An idea can simply be a vague concept, someone's opinion, a plan of action otherwise known as a roadmap, even a detailed image or vision formed by the brain. A concept is less well thought out, more obscure than a framework or model.
Evolution and thermodynamics were two of the great ideas of the 19 th century. The same goes for the great idea of the 20 th century - cybernetics. Still today many people have difficulty in comprehending these complex ideas. This lack of knowledge is a problem that some would attribute to poor education policy.