Ark is a cryptocurrency platform that has many advanced features. The video creator believes that it's undervalued and introduces ARK's features
Bitcoin Gold is a new fork of Bitcoin. To claim you have to import private keys to a Bitcoin Gold wallet. Beware of scam wallets. Importing a private key to a scam wallet, you can lose your BTC and BTG too. It is safe to move your Bitcoins to another wallet with different Bitcoin addresses, so in case of a scam wallet, the corresponding Bitcoin address has zero Bitcoins.
The blockchains need all transactions to be recorded on the blockchain. Raiden network, similar to lightning network, uses payment channels to make payments off-chain, It's very interesting to see how it works.