A good business case captures and documents the reasoning for starting a new project.
A business case helps to determine whether or not a project justifies an organizations investment into a project. This will also tells how the project will benefit the business and describe what the end state of the project should be.
The recommendation section summarizes the approach for how the project will address the business problem. It also describes how desirable results will be achieved by moving forward with the project.
The justification section justifies why the recommended project should be implemented and why this is selected among the various alternatives.
The problem statement describes the business problem. The problem may be anything like process, technology, product or service.