These two operators or function can be used to check equity of objects or operands. "==" is used to check if pointer values of objects are same. However "isEqual:" is used to test if both objects are having same values. So "==" works on reference and "isEqual" works on value. It can be easily understand by following example:

NSMutableArray *array1 = [[NSMutableArray alloc]initWithObjects:@"A", @"B", nil];
NSMutableArray *array2 = [[NSMutableArray alloc]initWithObjects:@"A", @"B", nil];
if (array1 == array2) {
        NSLog(@"==");
    }
if ([array1 isEqual:array2]) {
        NSLog(@"isequal");
    }

It will print "isEqual" because pointer values for both array1 and array2 are different

Second case:

NSMutableArray *array1 = [[NSMutableArray alloc]initWithObjects:@"A", @"B", nil];
NSMutableArray *array2 = [[NSMutableArray alloc]init];
array2 = array1;
if (array1 == array2) {
        NSLog(@"======");
    }
if ([array1 isEqual:array2]) {
        NSLog(@"isequal");
    }

It will print "isEqual" and "==" because reference and value for both array1 and array2 are same

Third case:

NSMutableArray *array1 = [[NSMutableArray alloc]initWithObjects:@"A", @"B", nil];
NSMutableArray *array2 = [[NSMutableArray alloc]init];
array2 = [array1 mutableCopy];
    [array1 addObject:@"C"];
    if (array1 == array2) {
        NSLog(@"======");
    }
    if ([array1 isEqual:array2]) {
        NSLog(@"isequal");
    }

It will print nothing because reference and value for both array1 and array2 are changed