Actual or potential, from not being generally known to or readily ascertainable through appropriate means by other persons who might obtain economic value from its disclosure or use; and is the subject of efforts that are reasonable under the circumstances to maintain its secrecy". Quite simply, it is any relevant bit of business information (device, formula or process) that business keep secret in a bid to get an edge over competing brands.
Examples include survey results, customer lists, computer algorithms and, in the case of Coca Cola, soda formulas. Unlike other forms of intellectual property however, trade secret cannot be protected by registration. It is up to you to come up with the necessary protective measures that will ensure that the information remains secret. Companies use many means like post employment restrictive agreements and covenants, restricted access to the piece of information, and legal measures like nondisclosure agreements to protect their trade secrets.