Prior to the 15th century European art had changed very little in hundreds of years. Then, over the course of the 15th - 17th centuries it took two strides forward as two new styles of art developed; Renaissance and Baroque.
The Renaissance (literally 're-birth') is said to have begun around 1400 when artists drew inspiration from classical antiquity and merged it with new developments in technology and learning. Helped by the development of the printing press, over the next 100 years Renaissance art and culture spread throughout Europe, taking on slightly different characteristics as it travelled. This spread of new ideas marked the end of the middle ages and the beginning of the modern age.
The painting is a realistic portrayal of a poignant scene. The grief in the faces of the two mourners (Mary and John) is quite clear