Usually planners get involved in the allocation and details of creating both public and private spaces for groups of people engaged in a wide range of variety of activities.
Recently, I learned some basic nomenclature about people gathering from my 16 year old son that seemed interesting about sizing a crowd.
He said that if I ever get a text message saying: "Hey, we're fill in the blank. Come on by." I could expect that this many people to be there:
Event or Activity Size
Chillin' or Hanging Out = 1-3 people
Having a Kick Back = 3-9 people
At a Party = 10 people or more
Now, if we account for the normal social pressures of school, dating, drugs, sports, parents, driving and the internet, then this simple form of everyday teen communication helps teens know what they are getting into and hopefully make responsible choices. For planners, it's nice for us to know that although language might change a bit; getting people together means pretty much the same as always.
There's probably a lot more technical information that can be written on this topic about design day criteria, instantaneous capacity, square footage requirements, security and long lines at bathrooms – but I have to leave now for an afternoon ‘kick back'.