User manual:Basic Settings
After clicking on the Basic tab, you can see following screen:
On this tab, you can change the label of your device, enable / change PIN, see the Total Balance and also view the XPUBs (Account public keys) of your accounts.
You can easily change the label of your device just by clicking on the Change Label button. You will be asked to confirm this action by pressing the button on your Trezor (and entering your PIN if you have PIN set up already).
Enabling / Changing PIN
To see a detailed description on how to choose and enter your PIN see Entering your PIN card.
The total balance of the entire wallet is visible here. Entire wallet means all accounts and addresses.
Account public keys let you view your accounts and generate new receiving addresses even when your Trezor is disconnected.