Behave is a subtle way of admonishing a child without drawing a lot of attention to you or the child. This makes the sign a great way to stop an escalating tantrum. A sharp look, along with the sign, can quickly alert a toddler that they are on warning without you needing to raise your voice or create a scene. It also gives the child a chance to correct their behavior before it gets out of hand.
As your toddler matures and is able to grasp complex ideas associated to behavior in social contexts, you can begin to introduce the sign for behave. We use it when visiting friends and also during religious services.