The geometric sequence is of the form a(n) = a*r^(n-1). For example, a(n) = 2*3^(n-1) with a = 2 as the starting term and r = 3 as the common ratio.
The variable n is in the exponent. We can replace it with x to get y = 2*3^(x-1); which graphs out to an exponential curve going uphill as you read it from left to right. This shows exponential growth, which matches with the growth of the original geometric sequence.
