Text Box objects provide fields for you to enter text strings. The text you specify can be data you want to retrieve from a data source or data that you want to write to a data source (to change the value of a tag).
When you configure a Text box, you can specify a data source that will retrieve data. If you want to write data to a data source, you must configure a WriteValue Command on the Text box's enter key event. Only real time data sources can be written to with the Text Box control. See To configure a Text Box to write to a data source for more information.