Tether is a cryptocurrency launched in 2014. It is a so-called stablecoin currently leading by market capitalization. Although according to the initial idea, each Tether was backed by $1 (that was going to keep the price of Tether stable), the company not always managed to maintain this price (at some point in October 2018 the price dropped to $0.9 per one Tether). Tether succeeds in terms of market capitalization and its price is almost all the time is really close to $1.
Ubiq (UBQ) is the mineable coin supported by the number of exchanges. Running the “Ethereum Virtual machine”, Ubiq provides developers with the tools to create smart contracts.
Ethereum Classic appeared after Ethereum hard fork in 2016. Just like Ethereum, the platform is capable of hosting smart contracts and serves as a virtual computing machine. The native token of Ethereum Classic is ether (ETC).