If you mean the dance scenes, you get them via getting all the Pink Cards and going on the quest for the Foil Pink Card. In order to get the stripper class, you need to have done the event with the bunny girl at Aurum Base and then have affection for the four main girls at 100 and have gifted them String Underwear (obtained by getting all pink cards), then convincing them to do it. This unlocks the stripper class for them. After that, just go to the area with the stage, and you should see a heart and which ones are available to do the scene with if you interact with said stage.
The context of the scene is that they are dancing on stage for you. That's it. Well, all of them besides Nyx anyways...
No one else comes in and sees it, obviously.
Once all of the dance events are completed, you can then get a fully "private" session with them (read: actively fucking them) via interacting with the stage again.
Also, the stripper job kinda sucks for combat purposes, like they can use a lot of weapons but have zero skills or magic besides a single skill that assassins get.
