slice in Rust

Slices are pointers to the actual data. They are passed by reference to functions, which is also known as borrowing.
For example, slices can be used to fetch a portion of a string value. A sliced string is a pointer to the actual string object. Therefore, we need to specify the starting and ending index of a String. Index starts from 0 just like arrays.
```
fn main() {
   let n1 = "Tutorials".to_string();
   println!("length of string is {}",n1.len());
   let c1 = &n1[4..9]; 
   
   // fetches characters at 4,5,6,7, and 8 indexes
   println!("{}",c1);
}
```
The &mut keyword can be used to mark a slice as mutable.