What it means when they say it's pouring buckets

This happened yesterday. I can easily say that it was the hardest rainfall I have EVER seen! The pictures don't do it enough justice. It started raining and then it started pouring, I looked out the front door (1st pic) and saw the water just pouring off the roof so I went to get my camera. My camera was upstairs which took me about 1 minute to get. By the time I came back down the whole front walkway was flooded!! In like 1 minute!!