preload behaviour

Hello

I need to understand something about preload feature on wpsupercache plugin.

I activated “Clear all cache files when a post or page is published or updated”, then I set preload every 24 hours. I am not sure how will this work together. Is preload unaffected by the first one?

I dont understand what this mean either “Preload mode (garbage collection disabled. Recommended.)”

Thanks in advance for your help

Naile