For each profile/device on which you use Brave and have Brave Rewards enabled, you have a “crypto wallet” that collects BAT. However, that BAT exists ONLY on that device. It’s not on any server anywhere, and there’s no way to back it up. If you have to reformat the device, you lose any accumulated BAT from that device. The only way you can use BAT directly from your BAT wallet is to tip content creators (Web sites) that have been verified by Brave and are able to accept BAT donations.
Once a device accumulates 25 BAT, you have the opportunity to transfer it to an Uphold wallet (PROVIDED you haven’t already linked four devices to the Uphold wallet). Transferring your BAT to an Uphold wallet is the ONLY way you can use it as “money” for other purposes and for other vendors. It’s also the only way to preserve your accumulated BAT if you change to a different device. However, as previously mentioned, Uphold wallets are limited to 4 linked devices. Period. If you change devices, you have still used up one of your four lifetime links and cannot regain it. In addition, I understand that Uphold charges exorbitant fees when you transfer from your Uphold wallet to another crypto system (Bitcoin, Ethereum, etc.).
In a few months, we will be able to use Gemini wallets instead of Uphold wallets to transfer our BAT to. I understand that there will not be a 4-device limit, a 25-BAT minimum to set up the Gemini wallet, and that Gemini’s fees are MUCH more reasonable than Uphold’s.