What is Autonomy?

Rather than turn off autonomy, why not just hit the pause button while you set up interactions for the desired Sim? This is how I play, as my grown daughter taught me. (Although, she never had autonomy on. Talk about a control-freak, that one.) It's a very useful tool, said PAUSE button. Not all games come with it. It's ingenious. I recall from Sims2, that if autonomy was shut off the Sim would end up standing, staring at a wall instead of using the toilet they so desperately needed. I haven't checked that out in Sims4.