Event - Notification
Many of the events share a notification mechanism. Here is a list of the types. Note that any alert can have multiple events of the same type, so you can set up a single alert to do something at any one or all of these times.
Each time alert conditions are met (repeating)
The event will happen every time conditions are met. This means the event will happen over and over again - on each sample that causes the alert to fire. In previous versions, this was the only supported notification type.
When alert conditions start (enters alert state)
The first time alert conditions occur, the event will happen. As long as the conditions continue, though, the event won't be repeated. This is a popular use - as you find out about new conditions when they happen, but don't have to be bothered again. As soon as the alert stops happening, then as soon as it starts again, this event will happen again.
When alert conditions end (leaves alert state)
This happens when network conditions improve so that the alert is no longer firing. As soon as the conditions move from bad to good (based on your settings), then this event will happen. A use of this is to have MultiPing email you each time conditions go bad (see above), and then when they improve again - but not to tell you anything in between.
Each time alert conditions are *not* met
This is the exact opposite of the first notification type above. As long as things are good on the network, this event will fire each time a sample is collected.