While we are not intervening in the nature of things, just look, listen, remember and learn about the world around us, we are seeing. Here are just at the time, as small child touches, breaks, or tries to toys on the taste, the parents of this kid with joy watching him, noting how he grows and develops. What is the "description"? When a person wants to talk about something other people or is he just saw something interesting and wants to always remember it, he describes this phenomenon with words or special characters – as best he can. Learn more at this site: Max Schireson. Describes the historical events – for posterity. It happens that people have to describe and does something not yet studied, but their descriptions to help others explore the previously described phenomena. What is an "experiment"? In cases where just watch becomes uninteresting, or observation impracticable for some "technical" reasons, to make experiments. To put the experiment on the subject or process, create special conditions and observed by interfering with the process by a specially established plan. If we formulate the basic question of the experiment, it would sound something like this: "What would happen if?" "And who knows – maybe poking his fingers into the electrical outlet, the child does, without knowing it, their first life experiment! What is a "theoretical level of scientific knowledge"? There are things you can not see, touch or measure the available human resources. For example, the distance from Earth to the sun not be measured in any ruler.