Relative sea level refers to the height of the ocean surface relative to the land surface at a particular location. It can be influenced by a number of factors, including tectonic movement, subsidence, and isostatic rebound. For example, if the land at a particular location is sinking due to subsidence, relative sea level will appear to be rising at that location, even if global sea level is not changing.
Eustatic sea level, on the other hand, refers to the global average height of the ocean surface. It is influenced by factors such as the amount of water stored on land in the form of ice and snow, as well as changes in the volume of the ocean basins due to processes such as plate tectonics and sedimentation. Eustatic sea level change can have a global impact on coastlines and marine ecosystems, while relative sea level change can have a more localized impact.