Text fields in Flash can be used for more than just entering text. There are three text options in the text panel:

static text: which displays text that you type normally in Flash

dynamic text: which uses a variable to stand in for text that you can send to the text field from an external text file or from another part of your Flash movie

input text: Which also uses a variable to get a value which is the text that will fill the field. The only difference with input text fields is that you can enter text into them to set a value for the variable that represents the text field.

Text fields are also very useful for checking variable values when debugging script (checking why somet hing doesn't work).

download the text field file shown above (file name: textfield.fla)
right click on the file (control-click for Mac) and select to download to your drive.