Renaissance means the "re-birth" of knowledge and culture. This period of rebirth in arts and sciences occurred in the latter 15th and all of the 16th century. The preceding epoch - the middle ages, is sometimes described as the 'dark ages', because the western world was embroiled in wars, mass migrations of peoples from one land to another, and a lack of stability. During the renaissance, explorers circumnavigated the earth (see the world events time line), painters dramatically changed their style to embody a great deal of realism, linguists rediscovered the secular literature written in the ancient languages of Latin and Greek, and the Catholic Church started to lose its stranglehold on people's lives, and its monopoly on learning..
The church of San Giorgio Maggiore, in Venice, Italy. was built in 1565, and is a magnificent example of renaissance architecture.
When applied to music, renaissance usually means music written between 1450 and 1600. Polyphony was developed during this period, and harmonies using triads were used, instead or the fourth and fifths used in the early middle ages.