What is photo metadata?
Cameras and phones store extra details inside each photo, called EXIF. It often includes GPS coordinates accurate to a few metres, the date and time, the device make, model and serial number, the editing app, and sometimes your name. Anyone who gets the original file can read it.
No quality loss
Only the hidden details are removed. The picture data is copied exactly as it was, so there's no re-compression and no change in quality, size or colour.
Rotation and colour
Phones often store photos sideways with a note saying which way is up. Keeping rotation leaves just that one note, so photos don't appear on their side. The colour profile only describes colours and holds no personal details.
Do social networks remove it?
Most large networks strip location from photos they display, but email attachments, cloud links, chat apps sending files, marketplaces and forums often keep the original file. Cleaning photos yourself is the only way to be sure.