The first one is set to Explicit, which basically means that the source won't be updated unless you manually do it.
For that reason, I have added a button next to the Text Box, which will update the source value on demand.
Try running the example on your own machine and see how the three textboxes act completely different: The first value doesn't update before you click the button, the second value isn't updated until you leave the Text Box, while the third value updates automatically on each keystroke, text change etc.
The other options are Property Changed, Lost Focus and Explicit.
The first two has already been described, while the last one simply means that the update has to be pushed manually through to occur, using a call to Update Source on the Binding.
To see how all of these options work, I have updated the example from the previous chapter to show you all of them: As you can see, each of the three textboxes now uses a different Update Source Trigger.
The item is deleted from the collection but the List View is not reflecting it.
The app has to be restarted to see that the item is deleted.
I'm setting this Items Source of the List Box programmatically: When I initially set the Items Source, the List Box (which is not visible at the time) gets its items set.