1. Promissory notes.
2. Secured loan notes.
Notes accompany financial statements (IAS) or accounts and may be required under the financial reporting standards or sometimes under relevant company or securities law.
Notes may also be included voluntarily by the company (or other reporting entity) to help - or arguably to hinder - understanding.
The latter argument - that excessive volumes of disclosure can hinder understanding - is based on the idea that the most significant financial information may be obscured by presenting too much other information around it.