For questions relating to the computation, estimation and properties of extremely large finite quantities that are not usually used in mainstream mathematics. This is not for questions that just have large numbers; the fact that a number is very large has to affect the question.
For questions relating to the handling of large finite numbers. This is related to googology, which is the study and nomenclature of large numbers.
To place a scale, numbers around the size of a googol and larger are considered "large".