Reza Rad provides an overview of what Power BI includes:
Power BI is a cloud-based technology from Microsoft for reporting and data analysis. This reporting technology is built in a way that is not only useful for developers to create reports but also for power users and business analysts. Power BI created a simple, easy-to-use, and user-friendly environment for creating reports. And on the other hand, it is based on several powerful components which help create reports and data analysis for complex scenarios.
Every component of Power BI is responsible for a specific part of the technology. There are components for building reports, connecting to data sources, doing analytics calculations, sharing reports, etc. The following sections explain what each component is. Some of these components are explained in detail in other articles.
Click through for a long list and a series of high-level summaries.