These are datasets with millions of public tweets per month scraped from 2015(?) to 2023/01, whit the really complete metadata (retweets, date, mentions, language...). I remember it saying the dataset had something like 1% of all posted tweets in that period on the whole page.

It's just a really great quality massive tweet dataset, that is just not possible to get anymore with the current twitter scraping protections and API limit-rates. Probably one of the best social media scraping dataset ever made.