[majewsky]

Many (most?) of the non-deterministic bugs in concurrent programs arise from two threads trying to write to the same place in the same time, or one thread writing to one place while the other thread just read that place and assumed that it was going to be constant for the moment.

Rust prevents that by having the concepts of "ownership" and "borrowing" built into the language. The Rust book probably explains this better than I ever could, but the basic idea is that you can only have one actor writing to a variable, OR any number of actors reading a variable. But you cannot have multiple actors having write access the same variable at the same time, or one actor writing to it while anyone has read access to it, unless you use some sort of serialization or copy-on-write mechanism.