A structure implementing the Send trait is safe to be moved between threads. This means that you can safely transfer ownership of a Send type between threads. The standard library implements Send for the types that can actually be moved across thread boundaries, and the compiler will automatically implement it for your types if they can also be moved between threads. If a type is only composed of Send types, it will be a Send type.
Most types in the standard library implement the Send trait. You can safely move ownership of a u32 to another thread, for example. This means that the previous thread will not be able to use it again and that the new thread will be in charge of dropping it once it gets out of scope.
There are some ...
