Vaults are where your money is held in your 1 Year Fixed Rate ISA for the duration of the 1 year fixed term.
A Vault is created on the day a new payment lands in your 1 Year Fixed Rate ISA – if you make multiple payments which complete on the same day, these will be held in the same Vault. Each Vault you have has its own interest rate and access date, and you can see all your Vaults listed in the app in Wealth > 1 Year Fixed Rate ISA.