The Filter Grid action provides a way to filter an already loaded grid. If possible, avoid using this action. For example - if the grid being loaded comes from an Execute Query Grid action, then modifying the query to perform the filtering at source will perform better. It is not always possible to run sufficient filtering at source - and this is why the filter grid action is present.
Filter Grid Editor
Grid to filter - The grid which should be filtered.
Filter expression - The filter expression to use. For more information about filter expressions, please see the filtering topic.