Memory card slots are used primarily to add external memory card to a phone. Extra memory in the phone can be used to store and transfer photos, videos, music, computer files, or backups of phone data such as the phone book and calendar.Some card slots support other functions, such as Wi-Fi connectivity or an NFC reader. This slot add features to a device. The SDIO supports that feature.

The memory card slot can be support two types of card SD (Secured Digital) and SDXC (Secured Digital extended capacity).The SD card  dimension should be 32 mm by 24 mm by 2.1 mm.  The card size exceeding the above dimension can damage the SD card slot if inserted.Also thinner cards, such as MultiMediaCards (MMC) were availble.

The Standard SD (Secure Digital) supports upto 4 MB to 2 GB, SDHC (Secure Digital High Capacity) supports upto 4 GB to 32 GB, and SDXC  (Secure Digital Extended Capacity) supports upto 4G B to 2 TB.