In order to represent an analog signal – such as a varying voltage or acoustic signal level – in digital form, that analog signal is sampled at precisely spaced intervals in time. In the case of CD audio, for example, the signal has been sampled 44,100 times per second, or at 44.1 kHz. In the case of a miniDSP unit with analog input, the analog signal is sampled at the sample rate of the plugin (48 kHz or 96 kHz, depending on the plugin). Digital inputs are re-sampled by an asynchronous sample rate converter (ASRC) so that the sample rate of the audio signal matches the sample rate of the plugin.
(Source: wikipedia.org)