Static vs global

If I have a C file like below, what is the difference between i and j?

#include <stdio.h>
#include <stdlib.h>

static int i;
int j;

int main ()
{
    //Some implementation
}

i has internal linkage so you can't use the name i in other source files (strictly translation units) to refer to the same object.

j has external linkage so you can use j to refer to this object if you declare it extern in another translation unit.

i is not visible outside the module; j is globally accessible.

That is, another module, which is linked to it, can do

extern int j;

and then be able to read and write the value in j. The same other module cannot access i, but could declare its own instance of it, even a global one—which is not visible to the first module.