The getList() method can be used for number of things, but the most frequently you will want to use this function in order to retrieve a list of options for a foreign key in the parent table.
input parameter is a table name that you are trying to query. Output is a dataset that if everything went well returns a datatable that has a name of the table that was passed in. If an error occured, the error table will be returned with the dataset.
The method can be used on a pretty much any table in the system, but you will use it the most frequently on those tables that contain options for foreign keys.