File Transfer Protocol.
In the beforefore times of moving larger files over teh Interwebz, most web server hosts had FTP clients that you could log into, create directories, and upload your data.
Nowadays, we have all sorts of cloud storage options like DropBox, Google Drive, WeTransfer, etc.
And unless a client specifically requires it, do not use Microsoft OneDrive. It is terrible. Maybe fine for Word docs and spreadsheets, but it is awful for media. Had a client send me several GB of footage to edit, and every time I downloaded the folder from his OneDrive I ended up with a ghost folder and media that couldn’t be read. Zipped, not zipped, it didn’t matter. Checked with some other post facilities and the universal response was, “Yep.”