OCR (Optical Character Recognition)
When your computer gets a fax or scans in text, all it sees are graphical bits on a virtual page. That text is not usable, searchable, or editable. If you pass the page through an OCR program, the software converts the shapes on it into a text document.
However, few documents are perfectly recognized and the errors are frequent if the type is small or the scan unclear. But the conversion is often faster than typing text manually.