Catch-in-focus. Read this if you are not familiar with this feature-
This feature is mainly intended as aid for manual focus lens, but it is useful for all kinds of lens!
On manual focus, if catch-in-focus is enabled, after setting a desired focus you press the shutter-
The camera will not fire until your frame is in focus (which might happen if the subject or the camera is moving).
For example - using this technique with fast exposure time you can have a really sharp photo of a speeding car with just a manual lens
ENJOY