The following are the Building Blocks (or) key components of Power BI:
Visualizations: Visualization is a visual representation of data.
Example: Pie Chart, Line Graph, Side by Side Bar Charts, Graphical Presentation of the source data on top of Geographical Map, Tree Map, etc.
Datasets: Dataset is a collection of data that Power BI uses to create its visualizations.
Example: Excel sheets, Oracle or SQL server tables.
Reports: Report is a collection of visualizations that appear together on one or more pages.
Example: Sales by Country, State, City Report, Logistic Performance report, Profit by Products report etc.
Dashboards: Dashboard is single layer presentation of multiple visualizations, i.e we can integrate one or more visualizations into one page layer.
Example: Sales dashboard can have pie charts, geographical maps and bar charts.
Tiles: Tile is a single visualization in a report or on a dashboard.
Example: Pie Chart in Dashboard or Report.