A Product Specification is a document containing all the essential information required to keep the teams on track and aligned with the product vision. The product specification contains information like

• What we are building?
• Who we are building it for?
• Why we are building it?
• What platforms or devices we are going to support?
• Expected distribution channel.

Apart from the above, it can also have other information which the initial discovery team thinks is important for the development team to know about.