can anyone please make me understand the "for " and "if " parts of this code...please explaain somewhat

Question

//its the code to remove the repetative ketter from a string

#include<iostream>
#include<cstring>
using namespace std;

int main()
{
int str;
string str1;
string str2;
cin>>str1;
for(int i = 0; i < str1.length(); i++)
{
if( (str = str2.find(str1[i])) < 0)
str2 += str1[i];

}
cout << str2 << endl;
return 0;
}

Answer 1

for int "i", so long as I is less than str1.length. The if should be
if ((str == str.find (str1 [i]))....