Ground pouring refers to placing a shape of copper tied to the net "Ground".
Some app notes and spec sheets refer to this when they want you to provide shielding just beneath the part. other times it is used to mitigate thermal issues by actually soldering the bottom of the part to a large copper area or using thermal tape or glue to contact the bottom of the part to this copper area. Ground pouring might be referred to in your ECAD tool as Area fill or plane (usually positive).
If you are using the ground pour (fill) beneath the part and they expect you to be soldering to it, be sure to include a soldermask and solderpaste opening beneath the part in the shape of the conductive underside of the part. also place vias in this area and be sure the board fabricator knows to fill them with conductive material, otherwise your paste will heat up and run down the vias.
for surrounding a trace with ground pour, they want you to encase the length of the trace with a guard net of ground. you can do this with an Area fill (ground pour) with vias tying it your ground plane or in if your ECAD tool has a shield command, you can use that.