what is the slot labled SC above the HD on my Latitude E6420

Notebook Dell Latitude 3410 Core i3 4GB RAM HD 500 GB Win 10 dell sc slot T54GY, 0T54GY LOC S1-1(NIA01 Genuine Dell Latitude 7490 Smart Card Reader Slot Cage and Circuit Board 0T54GY HUE 05 Smart Card Reader Slot Cage and dell latitude 3480 m2 slot Upgrade your laptop with a genuine lower bottom base case Perfect fit for Dell Latitude E5430 with a smart card slot Product Details Aquamoon Trading Shop

dell sc slot One SD-card slot Smart card reader One smart-card reader Power-adapter port One DC-in port Security-cable slot One wedge-shaped