Hi moonshine
Pension Credit is an income-related benefit made up of 2 parts - Guarantee Credit and Savings Credit. Guarantee Credit tops up your weekly income if it’s below £173.75 (for single people).
Since 15 May 2019 Pension Credits rules changed and is now based on the youngest of a mixed aged couple.
www.gov.uk/pension-credit/eligibility You are correct when you say your ESA will stop when your reach State Pension age. Pension Credit is a 'top up' providing you meet the qualifying conditions.
Gary