An information memorandum is issued to prospective investors of a project or business. It is for information purposes only. It is made available on the express understanding that it will be used for the sole purpose of assisting the recipient in deciding whether it wishes to proceed with a further investigation of possible investment.
It usually stipulates what confidentiality agreements applicants must sign/abide by because of the sensitive nature (such as information of value to competitors) of the material in the document or business plan.
It can contain much of the same information as a business plan but it also details such things as the process by which applications for shares will be dealt with, any pre-qualification tests for applicants and information about the business or sector in which the business operates.
Further reading on business planning
Advice on writing a business plan – make sure its fit for purpose