A3 Report - Standardized report developed as part of the Toyota Production System. The A3 names is from the paper size (approximately 11" x 17"). The report is written and drawn (illustrations are encouraged) on one piece of paper.
The "A3 problem solving process" is not just the single piece of paper. A3 (in the lean context) is about a method for process improvement which is very similar to the Deming improvement cycle. As one component of the Toyota Production the use of the benefit of the A3 report is a tremendous tool. As a separete tool, to apply without the rest of the system, it can still be useful but is not nearly as powerful.
The report should include something similar to (it can vary):