Gas and Altcoins

[Playboi]

I am really not understanding the concept of gas at all

I usually just use exchanges like Binance, Paxful, etc.

I'm experimenting with My Ether Wallet and I read that a transaction can fail if there isn't enough gas. Where exactly can someone get gas from?

Do all Altcoins that aren't on exchanges operate similar? Do you need gas to send an ERC20 altcoin from a hardware wallet to another wallet?