Sampling frequency, also known as sampling rate, refers to the number of samples taken from a continuous signal per second. It is measured in Hertz (Hz) and determines how accurately a digital representation can capture the original analog signal. Higher sampling frequencies can capture more detail, while lower frequencies may miss important information. In digital audio, for example, a common sampling frequency is 44.1 kHz, which means 44,100 samples are taken each second. This rate is often used in CDs and provides a good balance between sound quality and file size. Choosing the right sampling frequency is crucial for effective signal processing.