Exponential growth and decay

Compare the graphs of $y = 2^x$ and $y = 2^{-x}$. Since $2^{-x} = \left(\dfrac{1}{2}\right)^x$, the first grows as $x$ increases while the second decays.

The two graphs are symmetric about the $y$-axis: replacing $x$ with $-x$ swaps them. Both pass through $y = 1$ at $x = 0$, meeting at $(0, 1)$. The large dots mark that crossing $(0, 1)$ and the mirror-image points $(1, 2)$ and $(-1, 2)$.