What is the difference between "Activity$-$on$-$node" and "Activity$-$on$-$arrow" networks?

AOA networks often require dummy activities, while AON networks sometimes add dummy activities for convenience.

Nodes consume no resources or time in AOA networks.

Both are acceptable in practice, however Microsoft Project uses AON.

In AON nodes designate activities, in AOA arrows designate activities.

All of the above are true.