What in the Maps going on?

Can someone please explain whats happening here ( coming from a Java background ) this examples directly from the book:

use std::collections::HashMap;

let text = "hello world wonderful world"

let mut map = HashMap::new();

for word in text.split_whitespace() {
     let count = map.entry(word).or_insert(0);
     *count +=1;
}

println!("{:?}, map);

Returns

{"world": 2, "hello": 1, "wonderful": 1};

How are the values being incremented by count?

As I can't see count being referenced when assigning the values to the map?

Is this due to borrowing?