Rust: What is the difference between String and &str in Rust?

String — owned, mutable. &str — borrowed, immutable.

String:

• Owned type.
• Mutable.
• Heap allocated.
• Can be modified.

1let mut s = String::from("hello");
2s.push_str(" world");
3println!("{}", s);  // hello world

&str:

• Borrowed reference.
• Immutable.
• Can be stack or static.
• Cannot be modified.

1let s = "hello";  // &str
2let s2 = &String::from("hello");  // &str

Key differences:

• String — owned, mutable.
• &str — borrowed, immutable.
• String — heap.
• &str — reference.