What is the type of chip commonly used in android device as internal memory? Where the operating system resides, and often show up as sdcard0 (correct me if I'm wrong)?
Depends on the phone. They started using NAND, raw flash accessed directly. Then they moved to eMMC, NAND with an embedded controller for better performance. Recently, many have moved to newwer generation technology like Samsung UFS http://www.samsung.com/semiconductor/products/flash-storage/ufs/
Specifically, none of these are a type of EEPROM, a specific type of memory technology, that has no where near the memory density of NAND.