A const reference, denoted const auto&, has the ability to bind to anything. The created variable is always immutable. We believe that the const reference should be the default choice for variables you don't want to modify.
If the const reference is bound to a temporary object, the lifetime of the temporary will be extended to the lifetime of the reference. This is demonstrated in the following example:
auto func(const std::string& a, const std::string& b) { const auto& str = a + b; // a + b returns a temporary ...} // str goes out of scope, temporary will be destroyed
It's also possible to end up with a const reference by using auto&. This can be seen in the following example:
auto func() { auto foo = Foo{}; auto& cref = ...
