Because of the number of wings sticking out some of the view of the pilot is blocked which can preventhim/her from seeing other aircraft nearby which is a negative characteristic of a biplane.
American Eagle Rear Cockpit (Control Stick not shown)
On the positive side biplanes have a good roll rate making them very maneuverable. They generally have a low stall speed (the speed at which the lift being generated can no longer support the airplane in flight) and can fly on very little engine power.
Those involved in the very early development of the airplane were faced with having to build extremely large and long wings in order to create enough lift to put the weight of the airplane and its pilot into the air.
With the strength of the materials and design techniques available at that time along with low horsepower of the available engines, airplane builders were confronted with serious design challenges. A wing to support such weight was susceptible to structurally failing in flight which happened to a number of the designs. By building a biplane the length of wings was shortened considerably giving a way to design around these limitations.
By the end of the 1930’s engine power available had increased considerably, metallurgy had improved along with the engineering design of the internal wing structure so that the monoplane slowly took over and made the biplane obsolete for most purposes. Modern biplanes still exist today for special applications such as aerobatics and agricultural work.