Android phones, just like normal computers, use two primary types of memory: RAM and ROM. Although most users are familiar with these concepts, there is some confusion, however, when it comes to mobile devices.

RAM stands for Random Access Memory. It is volatile, which means contents are deleted when the power is removed. RAM is very fast to access and is used primarily for the runtime memory of software applications (including the device's operating system and any applications). In other words, it is used by the system to load and execute the OS and other applications. The number of applications and processes that can be run simultaneously depends on this RAM size.

ROM (commonly referred to as Android ROM) stands for Read-Only Memory. It is non-volatile, which means it retains the contents even when the power is off. The Android ROM contains the boot loader, OS, all of the downloaded applications and their data, settings, and so on.

Note that the part of memory that is used for the boot loader and Android is normally locked and can only be changed through a firmware upgrade. The remaining part of the memory is termed by some of the manufacturers as user memory. The data of each application stored here will not be accessible to other applications. Once this memory gets filled up the device slows down. Both RAM and Android ROM are often manufactured into a single component known as a Multi-Chip Package (MCP).