ICR, handprint and cursive
ICR stands for Intelligent Character Recognition: software reading hand-printed characters on a scanned page. Traditional forms constrain handwriting with letter boxes, so each character stands on its own, and ICR reads those well. For most forms processing that is the bulk of the work, and FineReader handles neat handwriting outside the boxes better than its reputation suggests.
Unconstrained handwriting is harder. In free-form comments, notes and cursive, letters join and run across the line. A cloud engine (AWS Textract, Microsoft Azure Document Intelligence or Google Document AI) or a language model reads these far better than a local engine, but not perfectly, so plan to check those fields. Flowing cursive prose, such as letters or long handwritten notes, is still where every method struggles.
Checkboxes and filled circles are read by mark recognition (OMR). Hand-filled forms are much of the work in healthcare, education and canvassing surveys. For how handwriting fits alongside the other recognition methods, see zone and dynamic OCR and every recognition feature. For job settings, see Handprint Recognition in the SimpleIndex wiki.