Both of these statuses grant the holder the right to remain in the UK on a permanent basis and will have been granted under the old systems in place before the EUSS was introduced.
Anyone with a valid permanent residence document must have applied under the EUSS by 30 June 2021 to convert this to settled status. If they didn’t their permanent residence will no longer be valid and they won’t have the right to remain in the UK.
Anyone with indefinite leave to remain will keep this status as there was no requirement for them to apply under the EUSS.