oh now I understand, but still why omni erc20?
USDT (Tether) just offer two different options to use their stable coin.
The first one, Omni, is a bitcoin blockchain token. It is somehow more secure than ERC-20, because it runs on the bitcoin network (which is more secure and robust, harder to suffer a 51% attack for example).
On the other hand, they also have a ERC-20 token (ethereum) and TRC-20 token (Tron). Those options are faster and cheaper to transact than the bitcoin token counterpart, however they run in less robust blockchains (specially the Tron one).
Tether cannot be mined for inumerous reasons, as any other stable coin, and this idea doesn't have any sense. To be a stable coin, your coin must be backed up by something. Tether is a token created by a company that works like a Debt Security.
You become a creditor of that company, making a loan to Tether with zero interest rate. You buy their token and tether promises to buy back that token for 1 usd each. You cannot make them out of thin air, only they are allowed to do so.
