So, Optical Character Recognition (OCR) is the process of recognizing computer generated text from an image, typically one that is scanned using document capture software. If you don't know the difference between OCR and Capture, see my other post here: OCR vs. Capture.
Intelligent Character Recognition (ICR) is the process of recognizing hand-printed or handwritten information from a scanned document. It utilizes the patterns of the pixels to match to specific written characters. This form of recognition is typically not as accurate as OCR, but there are several ways to make the accuracy acceptable, the main of which is to provide combed fields or spaced boxes to ensure character spacing, or whitespace between symbols.