Handwritten means put on paper with a pen rather than a keyboard. Somebody's actual hand made these marks.
That is the whole value of it now, since a handwritten note carries effort in a way a typed one cannot, which is why condolence letters and thank-you cards are still written by hand. Schools argue about how much handwriting to teach as keyboards take over. There is a legal sense too, since a handwritten will can be valid, and handwriting analysis is used in disputed documents.
1adjectivehandwrittenWritten by hand rather than typed or printed.
“There was a handwritten note tucked inside the book.”
From hand + written.
Etymology from Wiktionary, CC BY-SA