Most modern memory cards contain a single NAND flash chip and a smaller controller chip that provides a high-level interface to the data, implemented with a microcontroller that runs software which understands the host protocol (MMC, USB, ATA, ...) and abstracts the block allocation, bad block management, wear leveling and garbage collection that is necessary to be done on the NAND chip.
See also [https://lwn.net/Articles/428584/] for a detailed description of some of the concepts.
