Where information is original and not publicly known, it may be considered to be confidential information. If you need to disclose it to another, an obligation of confidentiality must be imposed on the recipient (preferably by way of written agreement) - this will allow you legal remedies against the recipient if the obligation is broken.
In certain circumstances, where trust is implicit in an arrangement (e.g. between a client and a professional advisor) that obligation may be implied even where there is no written agreement. With employees, implied obligations of confidentiality apply during employment - post employment restrictions in relation to confidential information should generally be expressly agreed in writing, preferably in the employment contract.