Short answers, pulled from the story.
Italian Renaissance painting is divided into the Proto-Renaissance (1300-1425), the Early Renaissance (1425-1495), the High Renaissance (1495-1520), and Mannerism (1520-1600). These dates represent overall trends and do not cover all painters, as individual artists' lives and styles overlapped these periods.
Florence is considered the birthplace of the Renaissance and of Renaissance painting in particular. The Medici Bank generated unprecedented wealth for the city, and Cosimo de' Medici established a new standard for arts patronage separate from the Church. The presence in the region of artists such as Giotto, Masaccio, Brunelleschi, Piero della Francesca, Leonardo da Vinci, and Michelangelo created an environment that elevated many lesser artists to extraordinary achievement.
Giotto (1266-1337) broke from the rigid Italo-Byzantine tradition by basing his figures on direct observation of life rather than on painterly convention. His figures were solidly three-dimensional, stood on the ground with discernible anatomy, and most importantly displayed visible human emotion including joy, rage, despair, and love. He is regarded as the herald of the Renaissance.
Masaccio more fully recognized the implications of Giotto's work than any artist before him and carried forward the practice of painting from nature. In the Brancacci Chapel, started in 1425, his Tribute Money fresco demonstrated a single vanishing point and a strong contrast between light and dark for three-dimensional effect. He died at 26 in 1428, but his work became a source of inspiration to Leonardo da Vinci and Michelangelo.
From around 1450, Italian artists were introduced to oil paint through Flemish painters including Rogier van der Weyden. Antonello da Messina likely learned oil techniques directly from Petrus Christus in Milan in early 1456 and passed them to Venetian painters including Giovanni Bellini during his stay in Venice in 1475-1476. When Hugo van der Goes's Adoration of the Shepherds altarpiece arrived in Florence in 1483, its naturalistic shepherds immediately prompted Domenico Ghirlandaio to paint his own Italian response.
Titian (c. 1490-1576) established colour rather than line as the major determinant in painting, applying pigment in patches with loose brushstrokes that brought out light and colour simultaneously. He dominated the Venetian school for over 60 years after Giorgione's death, introduced visual suggestion of movement in works such as the Assumption of the Virgin (1516-1518), and was the most sought-after portraitist of his time. In many ways he is considered the founder of modern painting.