This static variable will the global static variable to that file which has include the header file which contains this
Assume you have "test.h" header file where you have declare one static variable.
And another file "test.c" which included this "test.h" can be able to access the static variable( this static variable is only available to this file only i,e "test.c".
If some other .c file which is dependent on "test.c" try to use "exter key word" to use this static variable, it won't be possible because of the "static key word"
So this variable only is available for .c file which included that heard file which contains the static variable.