A situation that occurs when two distinct pieces of data have the same hash value, checksum, fingerprint, or cryptographic digest.
A unique identifier used to retrieve a paired value
|Space vastly larger||
"But if your key space is vastly larger than the number of targets you ll have a sizable number of hash-collision where you ll have to check if the target stored there is really the key you re looking"
from question "If I have an array of keys M, and an array of targets N, how can I verify that M[i] exists in N before searching it?"