The term "cc" is commonly used as an abbreviation for "carbon copy." In the context of emailing, it refers to copying someone on an email so that they receive the message but are not the primary recipients. This feature allows others to see the communication without directly addressing it to them.
The term "carbon copy" originates from the use of carbon paper in typing, where a sheet of carbon paper would be placed between two sheets of paper to create a duplicate of a typed document. The abbreviation "cc" evolved from this practice as technology transitioned to digital communication.