Why in Rust you need to explicitly specify lifetimes and how does it work?

I just started learning Rust and came across the concept of lifetimes. Honestly, I don't understand why they need to be specified explicitly. In other languages, like C++ or Java, references and pointers work without additional annotations. Why does Rust force me to write `<'a>` and `&'a mut T`?\n\nHere's an example that confuses me. I want to write a function that returns a reference to an array element by index:\n\n```rust\nfn get_element(arr: &[i32], index: usize) -> &i32 {\n &arr[index]\n}\n```\n\nThe compiler says: "missing lifetime specifier". Why can't it figure it out on its own? I pass a reference to an array and return a reference to its element. Obviously, the lifetime of the returned reference should match the lifetime of the input array.\n\nOr here's another example. I want to store a reference to