How does the memory of a 64bit and 32bit processor work In this article, the author states that a 64bit processor can theoretically reference 2^64 bytes of memory. What does he mean by this statement, or rather the word, reference?

Also, I visualize the entire RAM to be divided into little memory cells, each having an n-bit binary number that represents a given instruction or value that is needed for running any program in the computer. Is this visualization right?

If it is, then
for a 64bit processor, what would be the number of memory cells in the RAM?
No, the author is wrong. 

I have used 32 bit processors that could address 64 GB of RAM. Memory is restricted by the number of address lines, multiplied by the number of bytes addressed by each individual value of address lines. 

Address space of one application was limited to 4GB, but you could have a dozen applications running at the same time, each using several GB. 

The author also seems to be quite ignorant of what processors and operating systems exist.