Reports are the medium to arrange and represent the data in a systematic way, to i.e. data are represented in the grid format having rows and columns. There are different ways in which a report can be presented. Matrix report is one the main report format in salesforce along with other reports (Tabular, Summary and Joined, etc). Its additional capability to group the data by both rows and columns makes it bit different from the summary report.
One should go for the Matrix report if they need to summarize two different types of data alongside each other, i.e user should choose for matrix report only if he needs to summarize and present complex data. It gives the privilege to users to group unrelated records by rows and columns.
As the data in this report is presented in table layout so it is easy to check the various intersections between data groups. We can also insert graphs in the matrix report. While creating the dashboard we can use the matrix report. The matrix reports can be useful for measuring the trends.
The Matrix report gives the users the most detailed view of the data. Matrix reports can have 20 rows to be displayed on the report. We can apply five formulas, and up to 20 field filters can be utilized in a single report.
With the help of a matrix report, we can check and compare the behavior of one data dimension against another one. Matrix report is sometimes addressed as "crosstab" report and it can be sometimes used to compare the related tools.
If you want to represent the overview of data say revenue and quality of the product sold, matrix report is the best decision. If you want to compare the two report formats like matrix and summary, then the matrix will always be easy to read and understand.