Al summed it up nicely, so all I have to add are some thoughts on why setting up for the option to bounce is useful.

I am personally a big proponent of the Kiel-Denmark opening as Germany, because I feel that the -option- of bouncing Sweden is too helpful a negotiation point to pass up, unless the opening negotiation of the game indicates that Russia is highly interested in getting along with you and neither England nor France show anything but hostility (this happens relatively infrequently, but it has compelled me to move Kiel to Holland a time or two, and reach for Russian backup).

A good Russia should understand that moving to Denmark does not neccessarily mean that you will stand him out of Sweden, and that in fact, you are sincerely hoping that it is not neccessary, because the stand out is only a move you want to consider under circumstances you wish hadn't happened to begin with:

1) you see the obvious signs of a nascent juggernaut forming, and want to ensure that it is, if not halted, at least slowed down to the point at which you can browbeat England and Italy into agreeing to help you and Austria deal with it.

2) As a negotiation tool to forestall a R-I alliance from attempting to immediately dismember Austria. In this case, you tell Russia something like "If it looks like you're moving on Austria right off the bat, I will stand you out in Sweden. If you leave Austria alone, I let you in" in the spring.

3) As insurance against a Russian Silesia opening. This one should require no explanation to the Russian. If he does something as irritating as going to Silesia on you, then he should expect not to get Sweden as a consequence.

4) To extract some sort of concession from Russia. If you already know England is going to be a problem, for example, you can offer Russia uncontested grabbing of Sweden and support in holding it if he helps you into Norway.

5) Russia looks like he is going to have too good a time in 1901 for some other reason not mentioned. In this case, the Sweden bounce can reasonably be construed as a way to delay him from growing too fast.

Note that in pretty much all of these cases, you don't want to be in the position where the bounce is neccessary, but you set yourself up to be in control of the 1901 fate of Sweden anyhow, because it is better to have that control and not need it than to need it and not have it.

Generally, I feel that Russia should also be willing to understand that you -want- to let him have Sweden, but need to make sure he is behaving himself in the rest of the map. If I'm in a game where Russia reacts to news that I am going to Denmark and want him to avoid unsavory behavior elsewhere by getting furious and promising to do what he can to ruin me instead of asking what I would consider good behavior from bears, then he and I were probably not going to get along well anyhow, and it's best not to give him the build.