A computer has blocks of memory and the memory can be addressed; kind of like the way street addresses point to the houses (memory blocks) in a neighborhood. A variable is similar to an address (greeting) and the value (“Hello world”) would be contents at that location/address.

A very general example which should in no way be taken as an absolute…

Suppose each block is 4 bytes and a valid address must point to the beginning of a 4 byte block (or even numbered house on one side of the street). Therefore, one way to represent “Hello world” might be 11 ASCII characters (bytes), so greeting might point to address 128, and the next/following variable would then be at address 140.

I’m skipping a lot here as this is very, very language, hardware dependent (among other things). Hopefully someone will find that useful; upon reading it, I’m unsure.