A value stream is everything that needs to happen to make and deliver a product to the customer, both the important things and the ones that are not so important.
Value stream mapping usually starts with a team making a map of how things are right now. This means taking a picture of how materials and information move through a value stream. Next, the team creates a map of how things will be in the future. This means a picture of how things and information should move through the process to create value.
Repeating this many times is the easiest and most effective way to help yourself and your coworkers learn to recognize what is important.
Value-stream mapping is often used in lean manufacturing. However, people in charge of businesses in any field can find it useful.