A bond is a savings account in which you will keep your money for a set period of time for a set interest rate. It means that you can’t generally access your money early with a bond.
A building society is a type of financial institution that provides mortgages and savings accounts to its customers (some provide other banking services as well). Many of a building society’s customers are also members – the society is run for the benefit of members rather than shareholders.
Interest is paid in “bands” for example if an account earns 1% up to the balance of £10K and 1.5% on a balance over £10K and the account has a balance of £25K, the first £10K will earn 1% and the remaining £15K will earn 1.5%.