I have not really come across the term currency yet. So I assume speaking of currency is wrong in at least one way. Instead texts mention tokens. So: If you want to create your own currency (on the Tezos Blockchain) it will live there as a smart-contract. TZIP-12 describes a unified standard how smart-contracts can interface to act as a currency. It is called “FA2 - Multi-Asset Interface”.

Tokens

• fungible vs. non-fungible
• how many tokens can be transfered?
• who can transfer tokens?
• what token type is supported?