I presume that you know that the "area under a curve", the area between the graph and the x-axis, between, say, x= a and x= b, is the integral of the function from a to b. In this case, there is only one x bound given but goes to 0 as x goes to negative infinity so that thethreelines, , y= 0, and x= 2 do bound a "region". The area is . Integrate and then take the limit as a goes to negative infinity.