what does it exactly mean to move data in phone storage and internal storage I am using a Micromax canvas turbo
it has 16 GB internal memory

so when I install an app ,
i get the option to move the app to internal memory card ,
and then ican move it back to phon storage

so what exactly does these both mean ,

how should we decide ,
what app to move , 

or any info regarding this movement
"Phone storage" is essentially your /data partition, the main space on your phone allocated to apps.

"Internal storage" sometimes means the same but, since they are being contrasted here, it likely refers to the internal "SD card" partition.  Likely both of them are on the same flash chip, just set up differently.

SD cards (and "cards") are sometimes mounted later in the boot process, so sometimes it can confuse some launchers and you end up with app shortcuts being removed from your home screen.  Services also might not start properly.  Otherwise, however, they are more or less the same.  You really only need to move apps around if you're running out of space or if you want to be able to wipe one partition without losing as much data.