for loop - What does this iterative function in C do? -

specifically, want walk through algorithm starting input pat = "aab" , string = "ababbaabaa". i'm having trouble figuring out going on inside of nested loop because i'm not proficient in c. function looks this:

int nfind(char * string, char * pat){   int = 0, j = 0, start = 0;     //   int lasts = strlen(string) - 1;  //    int lastp = strlen(pat) - 1;     //   int endmatch = lastp;            //    (i = 0; endmatch <= lasts; endmatch ++, start ++){ //     if (string[endmatch] == pat[lastp]){     (j = 0, = start; j < lastp && string[i] == pat[j]; ++, j++)     ;    }        if (j == lastp)     return start;    }   return -1;  } 

so when function called, we'll have i=j=start=0, lasts=9, lastp=2, , endmatch=2.

since endmatch < lasts, run loop. i'm not sure line if (string[endmatch] == pat[lastp]) means. i'm familiar if statements i'm not sure if they're asking if endmatch == lastp or if has character arrays. here appreciated.

maybe problem understanding comes lack of understanding of strings in c.

using [] square brackets operator allows access element @ index. shorthand write *(pointer + index). uses pointer arithmetics find address pointer + index * sizeof(subscript type), , gives direct (referencial) access element dereferencing pointer.

a string in c represented character array finished null character. pat[lasstp] char type @ position lastp in string pat.

note:
1 needs note there difference between char array[20]; , char* pointer = __alloca(20); (or whatever exact way space stack). want point out difference between array type , "decaying" of array type pointer type wherever compiler thinks pointer thing can work with, when array type ill fit.
ref: arrays decaying pointers
, what array decaying?
subtle detail though, problem today more basic.