What is the difference between String and &str in rust?
In Rust, String and &str are two different types that represent strings in different ways.

String is an owned, heap-allocated string type. This means that a String is a standalone string value that you can manipulate and control as you like. When you create a String, it will allocate memory on the heap to store its contents, and you are responsible for freeing this memory when you're done with the String.

&str is a string slice type. A string slice is a reference to a portion of a string, rather than a standalone value. This means that when you use a &str, you are not responsible for managing the memory associated with the string data; the data is stored elsewhere, and the &str is simply a reference to that data. This makes &str more lightweight and efficient than String, especially when you're only looking to access a small portion of a string.

In general, it is more efficient to use &str whenever you don't need to modify the string, as &str is a reference type and does not require heap allocation. On the other hand, you should use String if you need to modify the string data, as String is an owned type and provides methods for modifying its contents.