I've never seen 25/25...that would mean the chart was calibrated for 25 feet instead of 20, or 15 , or 10 feet like normal.
But if you were told 25/25 , then that would be identical to 20/20
That would mean you can see at 25 feet what a normal eye should see at 25 feet.
20/20 means you can see at 20 feet what a normal eye should see at 20 feet.
25/25 or 20/20 doesn't mean perfect vision. It is just what normal vision should be.