Difference between INTERNAL SD CARD and Internal storage.
I m confused abt the difference between "INTERNAL SD CARD" and "Internal storage". I have 12 GB shown as INTERNAL SD CARD and 1 GB as Internal storage in "storage" settings of android.There's NO Micro SD card inserted.I didnt attach any external micro SD card.
I find "move to tablet" and "move to SD card" options for the applications installed. My Internal storage is almost occupied, so I wanted to move app from "Internal storage" to "INTERNAL SD CARD" using "move to SD card" option but it says "not enough storage"."INTERNAL SD CARD" has 100 mb available. Why cant I move data between these two internal storages.
Answer
The storage in your device is partitioned, so as example I have 32GB of storage:
name | fs type | size
/system | ext4 | 591MB: is the partition where the ROM is stored, it's mounted read only so you can't normally write there
/data | ext4 | 1.5GB: is the partition called "Internal storage", it's used to store apps and it's data.
/storage/sdcard0 | vfat | 27GB: it's an emulated sd card, so even if it's part of the same physical storage it's seen by the os as an sd card.
then there are other minor partitions.
Some manufacturers choose to not enable move to sd card for the emulated sd card, some enable it, it's not a bug just a choice.
As for your question, you didn't mention how big is the app you want to move and also to move an app to sd android creates a file that it's an encrypted ext4 filesystem which contains the app, so it might require more space than the original app size plus maybe there are checks to leave some free space in the sdcard.
To have a quick look at how your storage is partitioned you can install from Play Store "Partition Table" or the program mentioned by @Lunation Studios