Cell<T> provides compile-time unchecked mutation while RefCell<T> enforces borrowing rules at runtime to prevent data races.
Cell allows mutation without borrowing checks at compile time but requires unsafe code for interior mutability, while RefCell enforces borrowing rules at runtime and panics if violated. Use Cell for simple, atomic-like swaps and RefCell for complex interior mutability where you need to borrow data.
use std::cell::{Cell, RefCell};
let c = Cell::new(5);
c.set(10); // No borrow, just set
println!("Cell: {}", c.get());
let r = RefCell::new(5);
let mut borrow = r.borrow_mut(); // Runtime borrow check
*borrow += 1;
println!("RefCell: {}", r.borrow());
Cell is like a safe box where you can swap the contents instantly without asking permission, but you can only see the whole thing at once. RefCell is like a library book you can borrow; the system checks if anyone else is using it before you take it, and it crashes if you try to break the rules. Use Cell for simple counters and RefCell when you need to read or modify parts of data safely inside a shared structure.