The general concept of shielding, blocking EMI, makes sense. But, what allows a cable to fit under that category? Are there certain types of materials that must be used? And how do you shield a connector?
A shielded cable has a metalic covering. The covering can made of braided wires having a specified thickness and coverage percentage.Metal foil is specifed by thickness.
A shielded connector is made of metal or metalized plastic. Maximum shielding is obtained with a 360 degree circumferential connection between the connector shield and the enclosure or circuit board ground. The same applies to the cable shield; it should contact the shielded connector over a full 360 degrees.
Plastic parts can be coated with metal, a process called metallization, for both aesthetic and mechanical purposes. Visually, a metal coated piece of plastic features increased gloss and reflectivity.
Most plastics are not inherintly electrically conductive, but can be made so through the process of metallization.