The graph above is of some random signal, with an amplitude, or strength, of 1. This signal has a period of p (a period is the amount of time before a wave repeats itself). We might let a signal with amplitude 1 represent a binary 0.
This is the same sound wave as above, because it has the same period p. However, this signal has a higher amplitude of 2. We might let a signal with amplitude 2 represent a binary 1.
This is what amplitude modulation looks like. Notice that the period is the same for the entire signal, and that only the amplitude varies.
Assuming amplitude 1 = binary 0, and amplitude 2 = binary 1, this signal would represent 0011010.