What should requirements for a product consist of? What would you include first?

The product requirements should include the following key elements:

• Goals and objectives of the product — what exactly the product is supposed to solve.
• Functional requirements — specific functions and capabilities that the product must have.
• Non-functional requirements — performance, security, usability, etc.
• Constraints and assumptions — technical, business constraints, usage conditions.
• Acceptance criteria — how the success of the requirements implementation will be evaluated.

First and foremost, I would establish a clear definition of the goals and objectives of the product so that all participants understand what problem the product solves and for whom it is intended. This is the foundation for all subsequent requirements.