Internal memory is the memory where all the data of the mobile device is stored, the operating system, applications, photos, videos, music, chats, are stored in this memory so it is important to know if the device we are going to buy has of enough storage space for our needs.
The internal memory in mobile devices is equivalent to the hard drive in computers.
16 GB of internal memory today is a very small amount for a mobile device since only the operating system and updates can occupy half of this storage space, so we will have very little space to install applications. Even having our documents in the cloud 16 GB it is very little space and therefore it is already considered obsolete for Android and iOS mobile devices.