They implement the different address types?
Yes, even in legacy HD wallets, each private key derives three different address types in exception to TapRoot.
In Descriptor wallets, each address types are derived from their corresponding descriptors which are pre-generated when the wallet is created.
The math is defined in BIP32:
https://github.com/bitcoin/bips/blob/master/bip-0032.mediawikiYes, that's what they look like. When you talk about "change", do you mean the Bitcoins, which are transferred to yourself if you do not spend the total amount in the inputs? This is the path with the "1" (m/84'/0'/0'/1) I think.
If I set "External / Internal" to "1" in the BIP39 tool, the path changes and other addresses are generated. These are then the internal addresses for the change?
Yes.
You can get more information in BIP44; in BIP39 and BIP84, only the "
purpose" field is different.
BIP44:
https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki