Is it that the "link application to ram" idea is that we can easily start debug application which usually runs in flash ?
Isn't it possible to debug application in flash ?
It is for running your application in RAM instead of FLASH. That was necessary in 'old' days if you only were able to program the FLASH a few time until it weared out. Another benefit is that on some targets running the application in RAM is faster, but in that case you probably want to have the code in FLASH and then copy it to RAM at runtime.
I hope this helps,