What is the difference between the Mercalli and Richter scale?

The Mercalli and Richter scales are both used when measuring the impacts of seismic activity. However, while the Richter scale measures the magnitude of the earthquake (meaning the force of the earthquake), the Mercalli scale measures the physical impact of the earthquake within a given location. To put this into an example, an earthquake could have a Richter Scale recording of magnitude 5 meaning it is a moderate strength earthquake, however, given the Mercalli scale measures physical damage, it could have been recorded as a major earthquake of VIII on the Mercalli scale for example. This difference between the two scales, could occur in an area where buildings are less resilient- as a same magnitude earthquake could have different physical impacts on the environment depending on where the earthquake occurred.