Glossary of Printing Terms:
Carrier

In reference to direct mail, it is the package used to hold the pieces to the direct mail program, such as an envelope, box, tube or polybag.

In reference to integrated and affixed products, it is the continuous or laser sheet that the card or label is affixed to or integrated into.

In reference to pressure sensitive labels, it is the layer that holds the adhesive and facestock until time of application. Also referred to as the liner.