Descriptive analytics is a form of data analytics that looks at data statistically to tell you what happened in the past. It helps a business understand how it is performing by providing context that will aid stakeholders in interpreting information. This context comes in the form of data visualizations like graphs, charts, reports, and dashboards.
How can descriptive analytics help in the real world? In a hospital setting, say that an unusually high number of people are admitted to the emergency room in a short period of time. Descriptive analytics tells you that this is happening and provides real-time data with all the corresponding statistics (date of occurrence, volume, patient details, etc.).
If you want to take your analysis a step further, you could use diagnostic analytics to answer the question: Why did this happen?