While the first time deposit bonus is something that all of the online casinos have, some casinos will go beyond that and offer a reload bonus as well. What a reload bonus is essentially is a bonus that you can use after you have already made your first deposit. You can go ahead and use the reload bonus when it is offered to you to make another deposit that has a bonus attached to it. Without a reload bonus, getting another bonus on your second, third or fourth deposit would not be possible.
The reload bonus was put in place by online casinos that wanted to keep their customers after the first bonus had run out as they were finding customers going to other casinos to get their deposit bonuses once the one they were using had run out.
There are some very serious and easily measurable advantages to the reload bonus and it really depends on the type of gamer you are which advantage applies to you. If you are an avid bonus collector that is used to going around to different online casinos, chances are at some point you are going to be exhausting those first time deposit bonuses. The reload bonus concept allows you to go to different online casinos multiple times without having to worry that the bonuses you take are going to run out. This allows you to keep on collecting bonuses at regular intervals and since some people will even make their living doing this, the advantage is quite obvious.
In addition to that however, another advantage is one that applies to casino players that have been playing at a specific casino with the casino bonus. If that casino player needs the bonus amount to have a high enough bankroll to play, then reload bonuses will provide them with that exact same opportunity. This means that they can stay at one casino for a very long time and they do not have to relocate every time a bonus runs out (something that can be very annoying for a person to do).
If you are just a normal person that does not really need the bonus offer, but is glad to get it nonetheless, then the reload bonus is advantageous in the same way the deposit bonus is advantageous. That is to say that if the first time deposit bonus was welcome news, then getting another bonus for doing the exact same thing is going to be welcome news as well.