What are "cached tools"?

I am looking at the details for the GitHub Actions virtual environments, e.g.:

Each one has a section called “Cached Tools.” What exactly does this mean? I assume it means they aren’t installed by default, but that they are cached somewhere for fast installation when necessary, but how do I access them?

Are these just the tools that are installable with actions like actions/setup-python, actions/setup-ruby, actions/setup-node, etc?

Basically yes, though I don’t want to rule out other uses. Most of thesetup-* actions can install non-cached versions, too, but using the cached ones is much faster.

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