Because Word (Excel, Powerpoint etc.) is an OLE client and Barcode Creator is an OLE server, Word stores all the drawing information in its document when you paste it, not just the picture you see. This is called Embedding. All properties of the drawing are embedded in Word document, and you can revisit the drawing later on.
If you double-click on the Barcode drawing in Word, it will launch Barcode Creator and you can edit it through Barcode Creator.
Using embedding approach, it increases the size of the Word document. When there are many barcodes in a single document, it slows down the program. An alternative way is to paste the link only, through Word's paste special command.
When you double-click on the linked Barcode Creator drawing in Word, it opens the original Barcode Creator file, allowing you to edit it. OLE linking is useful if you want a drawing shared by multiple documents. It also reduces the document size. Changing the one linked drawing changes all the linked copies of the same drawing.