Your 24 word seed is your Ledger device seed which is used for restoring the Ledger. It is used in the Ledger Live app when you need to restore a device. Recall that the Ledger has your wallet private keys, not the Monero GUI application. Each Ledger device only uses one seed phrase; you do not have different seeds for each cryptocurrency you use your Ledger for.
Ledger has a full guide for using Monero with your Ledger and there is also a guide on StackExchange. There is also this guide for restoring a Ledger with Monero.
The long address you mention I can only assume is your wallet address, though I don't have a Ledger to confirm this.