Ok, Baking:
1- Baking to polygons= transforming a primitive (cube, sphere) into a polygonal object. Also used to transform abolean object made out of 2 different object into a single one. Same process for metablobs.
2- Illumination baking= the process of transforming the indirect illumination of an object into a texture map that will be applied to the object, saving incredible amounts of rendering time for animations.
If you were wondering about #2, it is only usuful for animations, and only when ligting conditions are consistent. The illumination baking process can be pretty long, but only done once for every object, which will save time on thousands of frames.
If you do still renders, no need for illumination baking.
If #1, transforming primitives into poloygonal objects is useless in Vue, since you cannot edit polygons in Vue. It's not a modeller. Baking metablobs and booleans to polygons on the other hand can lead to faster render times, but on rare occasions to errors in the resulting mesh.