Behaviors add extra capabilities to object types. They can be added with the Object Behaviors dialog. See the behavior reference section for more information on individual behaviors.
An example of a behavior is the Rotate behavior. This makes an object spin. Using behaviors for certain tasks helps speed up development and increase productivity. Behaviors are not intended to do everything in your project for you: timelines are generally preferable for pre-defined animations, and events are where your custom project logic is defined. Behaviors are essentially time-savers and shortcuts. Most behaviors can be replicated with timelines or events, but it can be more time consuming to do so. Behaviors are very customisable, including dynamically changing how they work in response to user input, but if a behavior isn't doing quite what you want it to, you can usually resort to reproducing it in a customised way with events.
All instances of an object type use its behaviors. You cannot add a behavior to only some of the instances - they all use the behavior - although you may be able to enable or disable the behavior for individual instances.
Some behaviors add their own properties to the Properties Bar. See the behavior reference for each behavior's properties
Some behaviors also extend the objects they are added to with their own conditions, actions and expressions. These are shown alongside the object's own conditions, actions and expressions in the Add Condition or Action dialog and Expressions dictionary.
Behaviors can also be added to Families Paid plans only. All the object types in the family then inherit the behavior.