Tether is a project linked to the USD so it is a cryptocurrency linked to the fiat currencies, the good thing is that it is completely stable, which makes it a currency for investment and protection of funds.
This currency is generally more stable than other types of currencies, it is not growing and brings with it good projects to get ahead, this is a good refuge to flee from the volatility of the current market. Tether is accepted on a wide variety of trading platforms and generally many other currencies are accepting the exchange of their currencies for this.