Active Sim Message!

Question, when you select a Child Sim, and you get a message that says, This is an Active Sim, what does that mean? This sim can't be given a command. What causes that?  

It means just that - that there are no interactions that the sim can have with itself; perhaps it has something to do with what the sim is doing and where the sim may be, such as a swimming pool, or a community lot. This message is usually seen with the toddlers too, and was also seen alot in the Sims 1.
  

Okay, thanks, Cinda! I thought as much, but wasn't sure.