Integration time is the length of time that the detector is allowed to collect photons before passing the accumulated charge to the A/D converter for processing. The minimum integration time is the shortest integration time the device supports and is dependent on how fast the detector can read out all of the pixel information. Integration time shou [..]

In an imaging device, the length of time during which the sensing elements are collecting charge between transfers to the transport registers. Also known as exposure time.

The time during which a pixel is being exposed to light. If there is an electronic shutter, the integration time is the shutter time. If there is no shutter, the integration time is approximately 1/frame rate. There is some overhead associated with reading the signal out of the pixel which must be subtracted from the integration time to be correct [..]

For a Sigma stills camera, Integration Time (EXIF 0x0423) is the exposure time (mechanical shutter open) plus the scan time (sensor to ADC). Deduced from testing.