Great question. Actually there are few types of integrated form/label products.
A form/label combination is manufactured by gluing two streams together with a seam. One stream is the form and the other stream is the label. While very effective, this is a more expensive product to produce and there is a relatively heavy glue line where the two materials are joined. This sometimes presents difficulty when the form/label is run through a laser or inkjet printer. Form/label combinations were much more prevalent in the impact printer days.
A piggy back integrated label is created by cutting a label patch and affixing it to the front of the form with adhesive. The liner of the label remains with the form after the label itself has been removed. Again, this is a good solution, but it too is expensive and the thickness of the patch makes for uneven packaging that can create unwanted curl and jam a printer.
A liner patch integrated label uses the form itself as the face stock and applies a liner patch to the back of the form. This reduces some of the thickness associated with the piggy back process and allows for a smooth face surface to print on. A patch typically does not hold a very tight tolerance and the patch itself may have an unglued edge that can catch in a printer.
Our integrated labels also use the face of the form as the face stock for the label, but instead of a patch, the liner is applied the entire width of the form. This allows for very tight tolerances and a very smooth, consistent glued edge so the integrated label runs through the printer without jamming. Also, the full width liner is less bulky than piggy back, or form/label combinations. It is very cost effective since the entire integrated label is applied in-line at high speeds as the form is being created.