It’s something that new Rustaceans struggle with, because most languages let you mutate whenever you’d like. The benefit of having this restriction is that Rust can prevent data races at compile time. A data race is similar to a race condition and happens when these three behaviors occur:
Two or more pointers access the same data at the same time.
At least one of the pointers is being used to write to the data.
There’s no mechanism being used to synchronize access to the data.
Data races cause undefined behavior and can be difficult to diagnose and fix when you’re trying to track them down at runtime;