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When you create a new wallet using ledger nano. It will display 24 word seed which we usually write on datasheet.

And with the 24 word seed you can recover the wallet? Where is the wallet saved online or on the hardware?

It's an hardware wallet but can be restored online or on New hardware device.

Yes an array of 24 random words when you set up, write them down in a couple of places for safe keeping. It is your only way back, suggest that you visit the site and run through videos available.