Difference between materialization_threshold and watermark

Hello TimescaleDB team,
May I know what are the differences between materialization_threshold and watermark? These terms seem to be describing about the same thing where data inserted after the threshold/watermark is deemed to be unmaterialized, and all data before threshold/watermark is materialized, at least this is what I understand from reading these two articles:

Is this just a rename?

I also see that in _timescaledb_catalog, there are tables called continuous_aggs_watermark and continuous_aggs_invalidation_threshold, where both tables have column watermark. I see that in continuous_aggs_watermark its referring to the materialized hypertable, while continuous_aggs_invalidation_threshold refers to the hypertable itself. May I know why is continuous_aggs_invalidation_threshold needed and why does hypertables need a watermark? I would imagine only materialized tables for continuous aggregates would need a watermark.

Would appreciate some insights and clarifications on this as I’ve yet to find any resources online that explains this.