Software documentation is written text or illustration that accompanies computer software or is embedded in the source code. The documentation either explains how the software operates or how to use it, and may mean different things to people in different roles. Documentation is an important part of software engineering. Types of documentation include: Requirements – Statements that identify attributes, capabilities, characteristics, or qualities of a system. This is the foundation for what will be or has been implemented. Architecture/Design – Overview of software. Includes relations to an environment and construction principles to be used in design of software components. Technical – Documentation of code, algorithms, interfaces, and APIs. End user – Manuals for the end-user, system administrators and support staff. Marketing – How to market the product and analysis of the market demand. Requirements documentation is the description of what a particular software does or shall do. It is used throughout development to communicate how the software functions or how it is intended to operate. It is also used as an agreement or as the foundation for agreement on what the software will do. Requirements are produced and consumed by everyone involved in the production of software, including: end users, customers, project managers, sales, marketing, software architects, usability engineers, interaction designers, developers, and testers. Requirements come in a variety of styles, notations and formality. Requirements can be goal-like (e.g., distributed work environment), close to design (e.g., builds can be started by right-clicking a configuration file and selecting the 'build' function), and anything in between. They can be specified as statements in natural language, as drawn figures, as detailed mathematical formulas, or as a combination of them all. The variation and complexity of requirement documentation make it a proven challenge. Requirements may be implicit and hard to uncover.