Modern cameras have several ways to lighten up images in an environment that does not allow much light to hit the camera sensor. Still, in many cases, it is easier and advised to use Flash instead to temporarily illuminate the scene. Especially indoor shots often require Flash for properly lighted and non-blurry photos.
When checking camera RAW files and other image files created by taking a picture on a camera or smartphone, exif information about whether Flash was used (on) or not (off) is often present. Depending on the camera, the type or mode of Flash is also given. This includes, among others: