The Renaissance, or "rebirth" was a time immediately following the collapse of the Middle Ages in Western Europe, generally dated around 1453, the year of the fall of Constantinople.
The primary difference between the two is the ways in which science and learning became separated from religion. During the Middle Ages, the prevailing philosophy was Scholasticism, in which only two authorities existed, the Bible and Aristotle. Aristotle was accepted because his theory that one element could be converted to another seemed to agree with the church's doctrine of transubstantiation, in which the Eucharist was transformed into the body and blood of Christ. Middle Ages learning was based on authority; experimentation was dangerous, as it might lead one into error, and thereby damnation. It was accepted that the universe was geocentric, and four elements existed, earth, air, fire and water. Furthermore, human beings were considered as corrupt and imperfect. Art of the period is generally representational, rather than lifelike. One need not prove the obvious, simply accept it on authority.
With the Renaissance, reason and experimentation became important. One did not accept authority unchallenged; rather one sought proof. An example of this is the use of ancient texts, including scripture written in the original Hebrew and Greek by Renaissance scholars. Experimentation was encouraged, and humans were considered the greatest creation and should be celebrated as such. This also is indicated in art of the period, which depicts human beings as very lifelike, almost as if they were photographed. Statuary of the period is often anatomically correct. The Renaissance did not reject Christianity; in fact many elements of it embraced Christian ideas. It did, however question authority and seek further proof.