Siri Suggestions iCloud- How do they work

[Irishappletech]

Hi just wanted to ask in relation to Siri Suggestions syncing across iCloud. First off when I swipe to the left I see the Siri Suggested apps do these sync over iCloud or not I am guessing no as the devices may have different apps on them. Secondly are the Safari Siri Suggested Websites Synced across devices. When I type www. ........... on Mac it will appear as "Siri Suggested" Website above it and I also see this on iPad and iPhone too. is this normal

In simple terms when it talks about machine learning what is machine learning and what exactly is being synced

Thanks
Sam