Displacement has both physics and chemistry meanings:
Physics - the shortest distance between two points.
Chemistry - a displacement reaction is where a less reactive element is removed in place of a more reactive one.
4.0L means it has a 4 litre displasement in the engine V6 means it has six cylinders in a v patern FI means it is fuel injected
The displacement-time graph for uniformly accelerated motion is a curve that is concave upwards. It starts with a less steep slope and gradually becomes steeper as time progresses due to the acceleration being constant.