Team 0% is attempting to clear every level in Super Mario Maker before the servers shut down on April 8. (New level uploads have been disabled since 2021, so there is no danger of new levels appearing at the last minute.) As of a few days ago, only a single level remains: Trimming the Herbs, uploaded in 2017 by Ahoyoo. (See also Ahoyoo’s original upload video.)
The level is short but extremely precise, requiring Mario to use Bob-ombs to precisely remove Piranha Plants and collect coins while navigating a tight space filled with spikes. There have been over 200,000 attempts so far! If you have a Wii U and feel like you might be a Mario master, this is your opportunity to pick up the final First Clear in Super Mario Maker history.
Forgive my ignorance, as even a quick search failed me, but what is a TAS?
UPDATE - thank you all for answering my question so well!
Tool assisted speed run. People write programs to run the game over and over, and by doing that they can prove or disprove potential strats, routes and such and then humans can try them.
Tool Assisted Speedrun
Using a script to automatically press all the buttons on the exact right frames so that you can automate a speedrun.