A visiting captain and Sisko never got along. This captain knows that Sisko is crazy about baseball, and spent some time studying the rules specifically to mess with him. They challenge each other to a game of baseball in the holosuite with their respective crews as the teams.
Now, Sisko needs to quickly teach baseball to a bunch of non-humans who don’t get what the big deal is. Hilarity ensues, and life lessons are learned along the way.
The commander of the space station loves baseball and they were playing a game against some vulcans.
EDIT: The reason that Worf (the guy in the gif) says this is because the commander said to "Make some noise" and this is the only kind of noise he really knows how to make.