Internal memory of Mobile Phone
It is a non-volatile storage, available in mobile phone which can be used to store photos, mp3, mp4 , videos, text files, and other user created files which you can access at any time, until it is deleted.
The Mobile Operating system (OS) is installed in this memory.
It is sometimes referred as ROM - Read Only Memory.
It is always good to refer as Internal memory rather than ROM. It is also sometimes referred as Internal storage or just storage.
Applications or apps are stored in the internal memory. Some mobile Operating system (OS) do not allow installing apps in external memory or memory card. Hence buying a phone with higher value of internal memory helps us to download more apps and save more files.
Mobile phone Internal Storage comes with 4GB, 8GB, 16GB, 32GB, 64GB, etc memory size.