One trillion bytes. Also TB, Tbyte and T-byte. See tera and space/time.
Although hard disks with a terabyte or more had been available for a number of years, in 2013, Kingston Technology introduced the first terabyte USB drive. As a transportable storage medium, this is the equivalent of 650,000 floppy disks, which were extremely popular up until the turn of the century. See USB drive.