Lol. You really don't know? Just google it. It's a file you download, in order to download another larger file.
The below is just my opinion, so your own due diligence is required - some, maybe all, might be factually inaccurate or incomplete.
With all the laws against software piracy to protect Tech Giant profits so Big Tech can use the money to sponsor deadly vaccines for the elimination and sterilisation of mankind, software pirates who don't want to support such genocidal tendencies are forced to use "peer-to-peer" file sharing software to download Big Tech software (I'm looking at you, Billy boy). A torrent file is one that communicates with the file sharing software so your computer knows which parts to download from the seeders, before putting the entire file back together on your computer.
Remember to use a Virtual Private Network if you're downloading software in a jurisdiction that may consider software piracy to be an offense.