Start with this FAQ, it will explain the basic terms and concepts. ( this is a clickable link)
That said, if your primary interest is security again I would recommend getting the SmartThings/ADT security panel model instead of the original smartthings hub. The original hub has a lot of weaknesses as far as security goes which the ADT model does not. Just as one example, if the SmartThings cloud is down (Which historically has happened about Once a month) Or your local Internet is out, the original model can’t send out any notifications at all, nor can you change the armed status on the system. The ADT model, however, has a cellular module for contacting the ADT monitoring center and can be armed and disarmed from the panel locally. There are other significant feature strengths as well.