A photo taken on a phone with location turned on records where you were standing, often to within a few metres. Posting it or sending it as a file can hand that to anyone who opens its details.
Taking a screenshot of a photo does remove its location, but it also lowers the quality and changes the size. Removing the hidden data from the file itself leaves every pixel exactly as it was.
Large social networks strip most of this on upload, which has taught people to assume it is always handled. It is not handled when you email a photo, send it as a file in a message, attach it to a marketplace listing or upload it to a small site.
One note is deliberately kept: the rotation instruction that tells a viewer which way up the photo goes. Without it a portrait photo would open on its side. It says nothing about you or where you were.
No. The picture data is copied across untouched, so the cleaned photo is pixel for pixel identical to the original.
Yes for JPG. Photos saved as HEIC are not read directly, so convert them with the HEIC to JPG tool first.
Yes, in your phone's camera settings. This is for photos you have already taken, and for files that came from somebody else.