The class template std::optional manages an optional contained value, i.e. a value that may or may not be present.
A common use case for optional is the return value of a function that may fail. As opposed to other approaches, such as std::pair<T,bool>, optional handles expensive-to-construct objects well and is more readable, as the intent is expressed explicitly.
Any instance of optional at any given point in time either contains a value or does not contain a value.
If an optional contains a value, the value is guaranteed to be allocated as part of the optional object footprint, i.e. no dynamic memory allocation ever takes place. Thus, an optional object models an object, not a pointer, even though operator*() and operator->() are defined.
When an object of type optional is contextually converted to bool, the conversion returns true if the object contains a value and false if it does not contain a value.
https://en.cppreference.com/w/cpp/utility/optional
https://en.cppreference.com/w/cpp/types/aligned_storage