The Table Customizer allows you to configure how you want the table to look to users. When you open the customizer, you'll notice that the data is formatted into different columns. The left column contains all the Table Customizer properties. For each column in the customizer, you can assign a header name, hide the column, make it editable and sortable, change the horizontal and vertical alignment of text, select a number format and date format style, and more.
If you want to test how the Table Customizer works in the Power Table, drag a Power Table on to your workspace, go to the Test Data property in the Property Editor, and check the 'false' checkbox. It will automatically fill the table with some test data so you get test out the Table Customizer.