The "Difference" tool in QGIS is often used to find the geometric difference between two vector layers. Here are the general steps to use the "Difference" tool:

Load Your Layers:

Open QGIS and load the two vector layers for which you want to find the difference.
Access the Geoprocessing Toolbox:

Go to the menu at the top of QGIS and select Processing --- Toolbox. This will open the Processing Toolbox panel.
Search for the "Difference" Tool:

In the Processing Toolbox panel, there is a search bar. Type "Difference" in the search bar to find the tool.
Run the "Difference" Tool:

Once you find the "Difference" tool, double-click on it to open the parameters window.
In the parameters window, you need to specify the input and overlay layers.
The "Input layer" is the layer for which you want to find the difference.
The "Overlay layer" is the layer that will be used to subtract from the input layer.
You may also need to specify an output file where the result will be saved.
Run the Tool:

After configuring the parameters, click the "Run" button to execute the tool.
View the Result:

Once the tool has finished running, you can load the resulting layer into QGIS to view the difference.