The distinction between `Rc<T>` and `Arc<T>` exists in the Rust world only to allow the Rust compiler to actually REFUSE to even COMPILE a program that uses a non- thread-safe primitive such as a non-atomic (thus susceptible to thread race conditions) reference-counted smart pointer `Rc<T>` with thread-bound API such as `thread::spawn()`. (Think 1-AM-copy-and-paste from single-threaded codebase into multi-threaded codebase that crashes or leaks memory 3 days later.) Otherwise, `Rc<T>`[1] and `Arc<T>`[2] achieve the same goal. As a general rule, many Rust interfaces exist solely for the purpose of eliminating the possibility of particular mistakes; for example, `Mutex<T>` `lock()`[3] is an interesting one.

[1] https://doc.rust-lang.org/rust-by-example/std/rc.html

[2] https://doc.rust-lang.org/rust-by-example/std/arc.html

[3] https://doc.rust-lang.org/std/sync/struct.Mutex.html