Yes that’s also true! For those who may be reading this and are don’t know how it works, a short dumbed down summary:
The Ethereum blockchain exists on a bunch of computers, the blockchain contains everything currently on the blockchain as well as a historical record of everything that’s happened. Building and maintaining that takes a lot of memory space and computing power. No one would want to help maintain that for free because it would cost you a lot of money every month. So to encourage people to store/process transactions, there’s a fee paid to these “miners” every time you make a transaction for them to add it to the blockchain, and that’s what the gas fee is. Miners are gonna process transactions that pay more gas because they make more money that way. Then it becomes supply and demand, as the network gets busier, gas fees go up. You can manually adjust the gas fee, if you pay extra your transaction will happen faster, but if you pay lower it could take a longtime before your transaction goes through (until no one is offering higher gas than you), too low and the transaction will never happen. That’s why late at night/early morning is cheaper because there is less blockchain activity, ‘supply’ is low so the gas fee miners can charge goes down.
Anyway hope that is clear as mud for how that works for those that don’t know. That’s of course a simplification and if I got something wrong someone who knows more please jump in and correct!