What’s the Auto Cool Down Phase on a tumble dryer?

I know this is such a random question but now the weather’s getting cool I’m struggling to keep up with our washing and looking into tumble dryers. I’ve never had one so am a bit clueless.

Some have the ‘Auto Cool Down Phase’ and others don’t. Just wondering what this is for/does? Is it necessary? The one I’m looking at buying is quite expensive as I need grey but doesn’t have the cool down phase.