Data is often stored in an array, which is a set of consecutive chunks of memory. Oracle's caches are often predefined arrays. The array is not big enough to hold everything. So Oracle takes that thing and applies some mathematical function to determine which chunk of memory, or the cell in the array, will hold the thing. This mathematical function is called a "hash function." This function returns an index to the array, which is commonly called the hash value.
This was first published in March 2007