The renaissance style originated in Florence, with Filippo Brunelleschi, but has spread to many other Italian cities, and also to France, Germany, England and Russia. Renaissance architecture was based around symmetry, proportion, geometry. Orderly arrangements and use of different pieces replaced the more complex aspect of medieval buildings.
The plan of a Renaissance building is square and symmetrical, and most commonly has the design to have a façade. One of the first true Renaissance façades was the Cathedral of Pienza. (below)
Aside from the facades, other characteristics of Renaissance architecture were the Roman orders of columns that include Tuscan, Ionic, Doric, Corinthian and Composite, which can be used for either useful (structrual) purposes, or just for decoration. More characteristics of Renaissance architecture are the semi-circular arches, semi-circular vaults, and domes. Dome of St. Peter's Basilica in Rome
The style of Renaissance architecture can be seen through the ceilings, which were flat or coffered, the doors, which usually had square lintels, the windows, which may be paired and set within a semi-circular arch, and the walls, which were usually of highly-finished ashlar masonry, and the corners had rusticated quoins.
Church of San Lorenzo in Florence (you can see the use of the orders of columns)