If you have geographical data in your data set and you want to visualize then you can proceed with the map view under Tableau interface. You can see or visualize the geographical data in tables, bar charts, stacked bar charts etc. but for map view you have to select the map from 'Show Me' option. Let me explain it with one example like if you want to visualize the state wise sales from default superstore data set.
So first you need to drag and drop the longitude (generated) in columns shelf and latitude (generated) in rows shelf, Then States in Details under marks card and Sum (Sales) in size marks card. Then you can see the map visualization in tableau as shown below.
Here Size of the circle denotes sum (Sales), Larger the size of the circle higher is the sales. You can do it in other way also, where you don't need to drag and drop the things individually. For this first open the new worksheet and then you just need to double click on States first the double click on sales, then you will see the same visualization as shown above.
You can check tableau training for more details on tableau visualizations and Analytics in tableau Desktop.