What is Checksum?

A checksum is a small fingerprint computed from a piece of data, used to detect corruption. If the data changes anywhere, even by a single flipped bit, the fingerprint no longer matches. Comparing the fingerprint before and after a transfer tells you whether the data is still intact.

Think of traveling with five bags and counting them after every leg of the trip. Check in, count. Land, count. Reach the hotel, count. The count is tiny compared to the luggage itself, but the moment you count four, you know something went missing along the way