"Inside baseball" describes details or minutia of a subject so detailed or requiring such a specific knowledge about what is being discussed that they generally are not well known or appreciated by outsiders.

The term is typically applied to discussions of science, technology, entertainment, politics, or related subjects of which the public has some general knowledge, but whose inner workings do not need to be known in order to understand the concept as a whole. For example, a film critic may write a movie review using insider jargon, information, or understanding of which regular movie goers would have little knowledge or even interest (such as citing the director's previous themes expressed in their movies in relation to the one being reviewed, because of the director's fascination with a particular school of film making).