To demonstrate what merging is all about, we will take an example from the National Oceanic and Atmospheric Administration (NOAA) weather data. It provides an awesome minute-by-minute update of Shapefiles for your desire to download data. We will look at a one-week collection of weather warnings, and combine these with state boundaries to see where exactly warnings occurred within a state boundary.
The preceding screenshot shows us the polygons before the union operation in QGIS.