[c] Passing string to a function in C - with or without pointers?

When I'm passing a string to the function sometimes I use

char *functionname(char *string name[256])

and sometimes I use it without pointers (for example:

char functionname(char string[256])

My question is,when do I need to use pointers ? Often I write programs without pointers and it works,but sometimes it doesn't.

Assuming that you meant to write

char *functionname(char *string[256])

Here you are declaring a function that takes an array of 256 pointers to char as argument and returns a pointer to char. Here, on the other hand,

char functionname(char string[256])

You are declaring a function that takes an array of 256 chars as argument and returns a char.

In other words the first function takes an array of strings and returns a string, while the second takes a string and returns a character.

An array is a pointer. It points to the start of a sequence of "objects".

If we do this: ìnt arr[10];, then arr is a pointer to a memory location, from which ten integers follow. They are uninitialised, but the memory is allocated. It is exactly the same as doing int *arr = new int[10];.