The Account Properties feature allows accounts to be tagged with arbitrary name/value metadata. Users can add such metadata to their own accounts, or to other accounts. This is a very convenient way to provide additional information about your account (e.g. email or social media handle), or endorse another account as having specific permissions or other attributes (e.g. businesses can tag accounts as KYC verified at different levels, or as having reached certain status as a regular customer). Account properties are global, but must be set using the Ignis child chain.
Account Properties is a feature on the public blockchain Ignis and available to all child chains on the Ardor Platform