What EXIF data contains
Typical fields include the capture date and time, GPS coordinates (on phones with location enabled), the camera or phone model, lens and exposure settings, orientation, and sometimes a small preview thumbnail. Editing software may add its own fields on top, such as the program name or edit history.
The visible pixels and the EXIF block are stored separately inside the file. That's why a photo can look identical while carrying completely different metadata - and why stripping metadata never touches image quality.
When it matters
GPS coordinates are the sensitive part: a photo taken at home and posted online can reveal your address. Major social networks strip EXIF on upload, but email, cloud drives, marketplaces, and most messaging apps that send files 'as documents' pass it through untouched.