Locations are threads that always exist, and rarely get closed. Like, Oak's Lab for instance. If you go there, you would post in that location, you would not start a new threat.
This is only for certain locations that we want to be permanent, and more like landmarks. Like the Gyms, or Indigo Plateau. Overtime, we will add more, like if people keep frequenting the same Diner, or if a certain cave becomes really popular.
You can have multiple people in the same location, but not interacting with eachother. What this looks like is multiple thread posts but they're directed at other players. If you're unsure if your character can hear, or sees, or experiences something another player does, ask a storyteller in the Out of Character section. Create a thread for it.
Don't worry if a location starts getting long, they should be, and that's okay.