Effectiveness refers to how well the solution fulfills the problem.
Efficiency refers to how well the solution utilizes the resources.
For example, you want to paint your house and have to decide between using a small paintbrush VS big paintbrush VS your hands.
Both paintbrushes will be equally EFFECTIVE since they can both get the job done equally well. However, the big paintbrush will be more EFFICIENT than the small paintbrush, since it can do the same exact job but much faster.
If you compare the paintbrush VS using your hands, you will realize that the paintbrush is more EFFECTIVE since they are able to paint evenly and with better quality whereas your hands will make an uneven painting surface and leave fingerprints. Your hand will never be able to do the same job as a paintbrush and therefore it is less effective.