I think that greater specificity would help in this question. The use of documentation is primarily meant to reflect current conditions in any enterprise "on paper." In business, "documentation" can refer to many elements such as depicting expenditures, salary costs, and/ or projected earnings over time. Documentation provides a sense of transparency to all dealings and all status reports for any organization or endeavor. Documentation allows outside people to fully understand the direction or condition of any venture. In businesses, documentation can help better understand where a company is making progress and where improvement is needed. The idea of documentation is a clear communication of status, both present and potential. If there is a violation of public trust that has been breached, it usually refers to documentation that has not been properly maintained or done so in a duplicitous manner.
Documentation is a rather general activity meaning recording in a document form any useful information. Thus documents refer to any recorded information.
Traditionally documents referred to the paper records of any information such as contracts, certificates, forms and other papers used in routine business documents, and manuals. However, with the increasing usage of computers, the documents can also be in the form of electronic records.
The purpose of documentation in general is to make record information for use whenever required. The documents may be used for a one time and immediate specific use. For example a purchase order is a document used in this way. Other documents may be used for referring again and again. User manuals is an example of such documents. Still other type of documents are created and preserved for possible future use. For example, at the close of project, some history of the project may be documented just in case some one wants to study it in future.
Documents are also used a a proof of truth of certain facts such as decisions taken, instructions given and agreements reached. These documents are used as reference and for establishing the facts if and when required.