Exif data is meta data that is saved every time you take a photo. Be it with regular cameras or smartphone cameras. It may work with web cam too but I never tried it before so I don't know.
From what I learned, data saved varies depending on the device and currents settings when the image was taken. My android for instance, only camptures unimportant stuff aside for maybe date. I always have geo location turned off so exif data never contains my location when I take a photo.
Here is a neat article about exif data and how to modify or delete it. https://www.howtogeek.com/203592/what-is-exif-data-and-how-to-remove-it/
pic not actually photo taken by me.
iirc mspaint doesn't keep exif data, so a trick back in the ol' days was to just resave it with paint.
I'm pretty sure most modern art programs have an option to not save it.
I feel like it should also be mentioned that this only applies to jpeg and a few other files designed for photographs.
Pic related is Krita export options for metadata on JPG, I believe photoshit and GIMP can also turn if off.
Some people don't like it because photoshop '97 was the original one and every new version is just a little meaningless upgrade from the '97 version.
Some people hate it because it's expensive/because adobe is a shit company.
Some people hate it because it's popular.
Love it or hate it, it's as good as a tool as any other in the market.
Don’t forget that your camera sensor has unique patterns of pixel sensitivity that can allow purely bitmap-based tracking.