If you're on Windows, right click an image, and go into the properties. There should be a Details tab where you'll find a bunch of text fields that can be edited.

There's also data that doesn't even show in there. For example, your camera/phone could be set up to save its GPS coordinates in EXIF so that you can keep track of where the pictures were taken. Naturally, unless it's stripped from the file, that data can be seen by anyone who has access to the file.

Most image editing software should be able to delete any EXIF data, but there is also software that can mass-edit all of that stuff to simplify the process.