The first difference is that the Lure Module is attached to a PokéStop and is thus immobile. Also, the effect affects all trainers in range of the PokéStop, making this ideal for team members hunting together. Its effect, pink petals floating down from the PokéStop, can be seen on the Map View.
This item cannot be obtained from a PokéStop. However, it can be received by reaching certain levels, or by purchasing it from the Shop for 100.