I am learning Operating System but these words really confused me, I tried to search on the internet but could not find the exact difference between them? Can anybody help me out and clear my confusion?
Primary storage (also main memory and physical memory) are generally used interchangeably to refer to the memory that is attached directly to the processor.
Secondary storage is storage that is not directly connected to the CPU. The most common case of secondary storage is the hard disk.
You say searched on the internet without finding an explanation, however wikipedia seems to have a lot to say about computer storage http://en.wikipedia.org/wiki/Computer_data_storage