What is "knowledge management"? KM is, quite simply:
The conscious management and nurturing of the information a corporation knows or needs to know to achieve its business goals.
The information a corporation needs to know varies from corporation to corporation and from moment to moment. Influences on what information is needed include what information they already have, how they do business, who does what, how much they trust each other, etc...
Another very strong influence is what information is already being managed within the corporation. Many companies already have an employee directory (usually managed by HR or IT). So this may not be information that needs any additional attention. But the larger the corporation gets, the more they focus on organizational structure as a classification system -- both on the intranet and in the employee directory (where manager is more important than current role, say). The larger and more diverse the corporation, the harder it is to find out what is actually being done within the company. What projects exist, what was done in the past, who is working on them and what is their status? These are questions that can be vitally important but equally difficult to answer.
So, from a pragmatic standpoint, KM within any specific company often ends up being responsible for filling in the gaps between other existing programs, such as HR, the Program Management Office, IT Management, Quality & Standards, etc.
Finally, the scope of Knowledge Management is bounded by what a corporation needs to know to achieve its business goals. The boundaries of what can be known are limitless. But the resources to manage that knowledge are not. Even the knowledge within a small company is far beyond the capacity of any reasonable program to control or influence.
Whether information is knowledge or noise is contextual. Determining the relative value of information in different situations is a key starting point for -- and determining factor in the success of -- any Knowledge Management initiative.
More writings about Knowledge Management can be found on Andrew's blog.