"Renaissance means "rebirth" -- so what's new?
Artists and scholars of the Renaissance self-consciously believed they were innovators, that they had begun a fresh new era. They have convinced posterity too. They rigorously aligned themselves with antiquity and coined the term "Middle Ages" as that dismissable millennium of lull in between. Thus the "light" of the Renaissance they depicted as breaking through long dark night of Middle Ages: this was Petrarch's insistence and the subsequent myth. Lately, many scholars have taken to calling this period instead the "Early Modern" period, which makes a lot of sense for reasons mentioned far below.
From antiquity, the Renaissance arts took their classical models. The Renaissance is also said to mark the beginning of the individual's effort to free himself from the rigidity of medieval feudal society and the Church.
The dating for this period is difficult because it emerges and peaks at different times in various countries: in Italy the mid-1300s/1400s, especially in the visual arts; in England the late 1500s especially in drama. The Renaissance generally is seen to end in the mid-seventeenth century.
HUMANISM: Intellectually new is Humanism, a movement growing out of the "rediscovery" of classical literature, art, architecture, etc. This springs up in Italy first, and education now becomes based on the Bible and classical arts. The "Renaissance man" is "well-rounded," which means well versed both in the liberal arts and in practical matters. Humanism supposedly marks a revolt against the otherworldliness of medieval philosophy and religion and proposes to make people realize their capabilities as individuals. Their proper roles are those of action vs. contemplation. Creativity does become more personal, less anonymous: artists now even sign their canvasses. The artworks depict a zest for life in this world and sensory delight. Renaissance arts turn toward the world of the present: wealth-seeking, political solutions, explorations in science, art, and literature all as means of individual development. God is present but marginal in the works; "Renaissance Madonnas make it difficult to recite a properly devout Hail Mary" (because they celebrate earthly beauty).
THE REFORMATION: To cleanse the corruption and idolatry of the Church, attempts to break and "return" to pure Christianity emerge, with emphasis on scriptures, not tradition; on faith, not works. Luther nailed his "theses" on the church door in Wittenburg in 1517. The Reformation was born of and contributed to the break-up Christendom and to the secularization of society. Princely politics ascended over the Church, religion and nationalism began blurring (hence, much later, "Godless communists" vs. "Godfearin' people").
POETRY: Poetry is an adjunct, not a primary, occupation. It's political; you need patrons, or at least official approval. Publishing was overseen by bureaus (so you're always in trouble and danger). Still medieval is the notion of art as craft, but the rhetorical ornateness is pronounced and new. Conventions are typically treated self-consciously as such. Nature is to be improved on by device, art, arrangement: "artifice" was a word of praise. Elaborate and complicated verse forms also emerged.
OTHER: The new established merchant or middle class liked books of instruction, romances, religious tracts, sensational ballads. There's a distinct genre of Renaissance books concerning the training of the courtly person, the gentleman, the education of a courtier or prince, and the necessary duties and etiquette.
I think the most important feature of the Renaissance, and that which makes it logical to rename it the Early Modern Period, is the rise of consumerism that emerges with the merchant class. In Renaissance art and not in medieval you can find countless examples of what for lack of a better word I have to call "stuff." That is, portraits are of feast foods, or of the family dinnerware, or of some other group of the patron's stuff. Jonson lists all the stuff at an impressive feast in a poem. It's a matter of showing off how wealthy we are or how well we appreciate material things. It's conspicuous consumption -- something not only not considered artistic in the Middle Ages, but even a sin.
I suspect a good proportion of the above is paraphrased from:
Literature of the Western World, Volume I: The Ancient World Through the Renaissance. 5th ed. by Brian Wilke and James Hurt. Upper Saddle River, NJ: Prentice-Hall Inc., 2001. 1849-1864.