What “eject” actually does
A flash drive can appear finished before the computer has finished with it. To make saving feel faster, an operating system may temporarily keep data in memory, then write it to the drive moments later. It may also need to update file-system information—the records that tell the computer where files are stored.
Using the eject command tells the system to stop sending new work to the drive and finish pending writes. Once that process is complete, the drive is ready to remove.
When unplugging is most likely to cause trouble
The risky moment is during a write: while copying, saving, or otherwise changing files. Pulling the drive then can leave a file incomplete or, less often, damage the drive’s file-system records. An activity light can be a clue, but it is not a perfect indicator; waiting until a transfer has finished is more useful.
If you have only read files, or the drive has been idle since the last save, removal is generally unlikely to cause a problem. Modern operating systems often manage removable storage to reduce the chance that data is left unwritten, but they cannot make unplugging during active work harmless.
A practical rule
For a drive you use casually, the important habit is not ritualistically ejecting it after every glance—it is avoiding removal while files are being written. Ejecting is still the clearest way to ask the computer to wrap up any hidden work. If it reports that the drive is busy, close the files or apps using it and try again; that warning means something may still depend on the drive.
