Intermediate
Cryptography
Avalanche effect
A small change in the input produces a completely different hash.
In simple terms
Change one character and roughly half of the output bits flip. Similar inputs do not give similar hashes.
Analogy
Dropping a pebble that triggers a landslide: the tiny cause and the huge effect look unrelated.
Going deeper
Good diffusion (a term from Shannon) makes every output bit depend on every input bit. In SHA-256 the message schedule and round function spread a single flipped bit across the whole state within rounds — the measurable result is ~128 of 256 bits differing on average.
Common mistake
Never expect that similar inputs produce similar hashes.