You should use this to specify the columns that will appear in your panel.
If you wish a column to be displayed to an administrator, you will need to define a title.
If you are using the db_items property and wish the value of a column to come from a table in the database, you will also need to provide the column's SQL definition in the db_column property.
The column's code-name needs to match the code-name of the data in the items array of arrays to see the values.
columns: