how do if and else behave exactly?

an example from a book:

#include <stdio.h>                                                                                                  
                                                                                                                    
#define IN 1                                                                                                        
#define OUT 0                                                                                                       
                                                                                                                    
main()                                                                                                              
{                                                                                                                   
    int c, nl, nw, nc, state;                                                                                       
                                                                                                                    
    state = OUT;                                                                                                    
    nl = nw = nc = 0;                                                                                               
                                                                                                                    
    while ((c = getchar()) != EOF) {                                                                                
        ++nc;                                                                                                       
        if (c == '\n')                                                                                              
            ++nl;                                                                                                   
        if (c == ' ' || c == '\n' || c == '\t')                                                                     
            state = OUT;                                                                                            
        else if (state == OUT) {                                                                                    
            state = IN;                                                                                             
            ++nw;                                                                                                   
        }                                                                                                           
    }                                                                                                               
    printf("lines: %d\nwords: %d\ncharacters: %d", nl, nw, nc);                                                     
} 

suppose the input was stack overflow. here is my understanding of how this code will function:

1.getchar() will take s from the buffer, so c = 's', and add 1 to nc.

2.check if c is \n. if true, add 1 to nl.

3.check if c is a blank, a newline, or a tab. if true, state is 0.

4.'else if' state is 0, state is 1 and add 1 to nw.

my question is: in step 4, why is else if necessary? even without else, state should still be checked if 0, no? will the rest of the while body be skipped if one of the if checks are true? how do theses loops behave exactly?