Most images and photos are likely to be protected by copyright. This means that a user will usually need the permission of the copyright owner if they want to copy the image or share it on the internet.
The person who creates an image, such as somebody who takes a photo, will generally be the owner of the original copyright.
The length of the copyright period will depend on when the image was created. Generally speaking, copyright in images lasts for the life of the creator plus 70 years from the end of the calendar year of their death. That means that images less than 70 years old are still in copyright, and older ones may well be, depending on when the creator died. So in general a photo could still be copyrighted until it is over 150 years old.
Some people seem to think that just because an image is on the internet it is in the public domain, that is not correct.