If your question purely base on plastering work and you wish to know difference between them then,
When someone manufacture it in control enviornment and do sale it by packing even though its a plaster material, they say it as render.
Rendering means - a color shade or a consistent finish or a factory manufactured product.
Such renders provide uniform finish.
If you are doing plaster at site, you may get variation in color, sand size etc and workability issue which makes finishability of plaster to go difficult and sometimes result in bad finish.
Renders are engineered pre-mix products which have consistent sizes of materials + additives like polymers to ensure workability, pot life etc.
Render is also mean final finish, mostly external pre-mixed plaster are term as render.
There is as such no difference other than manufacturing process.
Plaster need to dash on wall using trowel and then need to be finish with float. Due to this it can be applied as thick layer.
Render can be applied as plaster or can be applied in thin layers by using small floats.
Render can be applied as in thick and in layers.
Render is finish coat in plaster, it can be smooth or textured finish as desired.