Understanding 'Constitutional Mootness' in Administrative Law

Yaar, can someone please explain 'constitutional mootness' in Administrative Law in simple terms? Our CUET PG Law textbooks make it sound like a complicated maze. I mean, we all know about the doctrine of mootness in general, but what about when it comes to constitutional rights and administrative decisions? For example, if a government decision is challenged in court, but the issue becomes irrelevant because the government has changed its policy anyway, is it still justiciable? Or is this scenario an example of constitutional mootness? Koi aap isse theek se samjhane ki koshish karen?