The Compose bar provides a "scratchpad" that you can use to write out short pieces of text and then copy them to the Phrase box, the Type Retranslation dialog, the Note dialog or any other place where you need to put them. The Compose bar gives you the chance to change and edit your words before actually placing them in the document.
To copy text to another location you must use the Clipboard. To do this, see Copying text to another location.