Bonds are loans to either companies known as corporate bonds or loans to governments known as government bonds or in the case of UK they are called Gilts (Gilt Edged Securities).
They pay interest on the loan (either fixed or inflation/index linked) and the loan/nominal capital value is paid back at redemption date.
Mini bonds are loans to companies on a smaller scale sometimes used in crowdfunding platforms where you buy a smaller share in hundreds or a few thousand pounds.
The FCA has banned the marketing and sale of mini bonds to consumers i.e. non professional investors where the loans to companies are companies that invest in either
This is partly due to a recent ‘high profile’ failure of a property development company that failed with little or no return due back to the mini-bond holders.