What’s the difference between tab sorting and user labels?

Tab sorting is automated classification by Gmail:

Gmail decides whether messages go to Primary, Promotions, Social, or Updates based on algorithmic analysis.

User labels are manual organization by recipients:

Users create their own labels and filters to organize mail. This is personal customization.

Users can override tab sorting by creating filters that label or move your messages. Their preferences override Gmail defaults.

You cannot control user labels. You can influence but not control tab sorting.

The port assigns your berth automatically. The merchant can reroute your deliveries to their preferred warehouse.