Core answer
Start here. This is the direct spoken answer to practice first.
Why this question matters
This question reveals whether the candidate knows async history and modern .NET behavior. The useful answer avoids both extremes: blindly adding ConfigureAwait(false) everywhere or saying it never matters.
ConfigureAwait(false) tells an await not to capture the current context for the continuation. In older UI apps and classic ASP.NET, capturing the context mattered because the continuation might need to return to a specific thread or request context. In ASP.NET Core there is usually no request SynchronizationContext to return to, so it is less important for normal application code. It can still matter in reusable libraries and UI applications.