For example, CD quality audio is sampled at a frequency of 44100 times per second. With one sample for each stereo channel. Each sample is 16-bits which can represent 2^16 = 65536 unique amplitude values for that point in time.
The highest frequency in the original sound that can be represented by the samples at a given sample rate without a kind of distortion known as aliasing is limited to half the sampling rate. See Nyquist-Shannon sampling theorem.
Also see sampler.