This is a Note Admonition. They are used to give you additionl information about the topic at hand.
This is a Tip Admonition. They are intended to give you a small but useful piece of practical advice.
This is an Important Admonition. This means the information is of great significance or value and should not be ignored.
This is a Caution Admonition. When you see these you should pay particular attention to the information and care should be taken to avoid mistakes.
This is a Warning Admonition. The information should be taken very seriously and indicates a possible problem, or other unpleasant situation may arrise if ignored.