Fn: a function that can be called many times without side effects. Can be shared. Almost exactly like regular functions besides the capturing. FnMut: a functio

Fn: a function that can be called many times without side effects. Can be shared. Almost exactly like regular functions besides the capturing. FnMut: a function that can be called many times but can have side effects, because of this it must be exclusively held (&mut F) FnOnce: a function that can be called only once, making use of by-ownership function calls So I remember it like Fn: just a function FnMut: a function that needs &mut access FnOnce: only used once, moving ownership