What is a matrix visually?
The matrix visual is similar to a table. A table supports two dimensions and the data is flat, meaning duplicate values are displayed and not aggregated. A matrix makes it easier to display data meaningfully across multiple dimensions -- it supports a stepped layout.
How do you read a decision matrix?
Decision Matrix Analysis works by getting you to list your options as rows on a table, and the factors you need consider as columns. You then score each option/factor combination, weight this score by the relative importance of the factor, and add these scores up to give an overall score for each option.