I am currently reading the solidty docs , and i came across this :
Mappings can be seen as hash tables which are virtually initialized such that every possible key exists and is mapped to a value whose byte- representation is all zeros: a type’s default value. The similarity ends here, though: The key data is not actually stored in a mapping, only its keccak256 hash used to look up the value. Because of this, mappings do not have a length or a concept of a key or value being “set”.
I understand what hash tables are , but i have absolutely no clue what the above means. What exactly does virtually initialized mean?
If a mapping was created as (uint=>uint) what would happen in this scenario? I understand the key refereced as a hash , but i fail to understand the concept. How is this computationally beneficial to the smart contract in terms of storage?