Raised Door Threshold
Raised door thresholds are usually pretty common in garages that are detached or even attached to houses.
In the picture above, the threshold was poured out of
concrete to replace the damaged garage footing.
If you're having a problem with water, let's say that this area floods or retains water for long periods of time and you don't want the water to go into the garage, the raised door threshold wouldn't be a bad idea.
If you are having problems with water in an area like this, it would be much better to fix the water problem than it would be to install a raised door threshold. These door thresholds are safety hazards and you wouldn't believe how many times you're going to hit your feet on them before you finally get used to stepping over them.
I don't recommend installing this type of threshold, simply because it's a safety hazard. If the house or garage is built this way, there is very little you can do about it, unless there is a way that you can remove it without harming the structure of the home.
Most of the time, you see this kind of construction when it was an afterthought or the foundation contractor made a mistake. Sometimes you can also run into this problem, when a new door was installed after the home was built, by remodeling contractor.