rvalue references: what exactly are "temporary" objects, what is their scope, and where are they stored?

rvalue references: what exactly are "temporary" objects, what is their scope, and where are they stored?

Reading some articles, rvalues are always defined as "temporary" objects like Animal(), where Animal is a class, or some literal e.g. 10.

However, what is the formal definition of rvalues/"temporary" objects?

Is new Animal() also considered a "temporary" object? Or is it only values on the stack, like Animal() and literals stored in code?

Also, where are these "temporary" objects stored, what is their scope, and how long are rvalue references to these values valid?