Build In
Build In is a part of the Motion settings.
The Build In motion occurs when the shot element is not in Live and will become Live. It only occurs when the Smooth transition is active.
Here is what the Build In controls look like:
From ...
The Popup controls where the motion begins.
For example, if you select "From Left" then the motion will begin from just to the left of the visible area of the broadcast.
Fade In
Controls whether the shot element should fade in.
If Fade In is unchecked, the element will "pop" into the Live, much like a Cut.
Spin In
The shot element is spun into position.
Scale In
The shot element is scaled in.
Decelerate In
All of the above actions are done performed in a way that makes them appear to slow down.