A card reader is an input device that reads flash memory cards.
By the way, it can also be connected to a standalone device from a computer via USB, or it can also be integrated from a computer, printer, or a multifunction device. At the same time, there are already built-in card readers in all multifunction printers/scanners/copiers.
Most card readers accept multiple memory card formats, including compact flash (CF), secure digital (SD), and Sony’s Memory Stick. At the same time, some card readers accept other formats like XD, SmartMedia, Microdrive, and Memory Stick Pro Duo cards.
The main job of a card reader is to read the data on a memory card. So when you insert a memory card into a card reader and connect it to the computer, it shows on a mounted disk.
Whereas if you want to see the contents of the memory card, then you have to double click on the icon of that card. This icon typically appears on the desktop (if we talk about Macintosh computers) while it shows inside “My Computer” (if we talk about Windows machines).
Similarly, if you want to remove the card, you must unmount or “eject” that disk before physically removing it. This saves your memory card from getting corrupted.