Recall:
Exponential growth is when numbers increase rapidly in an exponential fashion so for every x-value on a graph there is a larger y-value.
The exponent for exponential growth is always positive and greater than 1.
Decay is when numbers decrease rapidly in an exponential fashion so for every x-value on a graph there is a smaller y-value.
The exponent for decay is always between 0 and 1.
Hence Exponential growth is increasing function and Decay is decreasing function so this is a major difference between them.