There are two types of requirements that are gathered for any project idea: Technical requirements and Business requirements. Business requirements tell us WHAT a product is supposed to do, Technical requirements tell us HOW a product is supposed to do that thing. These two are often mixed up because they share the same main goal, which is to communicate complex ideas in an accessible manner.
The business requirement is not something a system must do, but something that needs to be done or have in order to stay in business. Without correct and complete data, the business would lose its customers fast. These requirements are generally written by someone who understands the business process and can translate them into writing. All these requirements are not necessarily to be translated to functional requirements, as most of the time if the person writing them does not have any technical background they are more likely to put in requirements that can’t possibly be filled. But regardless they provide a comprehensive idea of what needs to be done.
Technical requirements describe how a product needs to do something, and are mostly a translation of how to achieve the given business requirements. Technical requirements MUST be written by somebody technical (Surprise!) describing how the business would like a software system to work and proper steps required for making sure that the software is built properly. These requirements mostly explain two main things how the architecture of the product should work, and how it should interface with other systems and software.
Depending on the audience reading these requirements their reactions might vary, give a technical document to a client with no technical background and you will see confused puzzled faces, and go through long meetings where both parties come out very frustrated. On the other hand, provide a technical team with pure business requirements and you will get 101 questions on why these features are needed and how are they suppose to be linked together.
The main objective for both business and technical writing is to be useful, to inform, and help make an educated decision in purchasing or investing in developing a project. This is when the innovation, real change, creativity, out of the box thinking comes in, if you really understand WHAT a business does, then you can come up with the best solution for that business.