• Reference ellipsoid - An idealized ellipse around the Earth used as a proxy for the bottom of the ocean. The typical reference ellipsoid used by altimetric missions is 6378.1363 km equatorial radius and 1/298.257 flattening coefficient.
• MSS - Mean Sea Surface - The height of the ocean after averaging many years of sea surface heights to remove seasonal, semi-annual and annual signals.
• SSH - Sea Surface Height - Sea surface height is the height of the ocean above a given idealized ellipsoid around the Earth, known as the reference ellipsoid. SSH typically comes from a single instrument or a family of similar instruments such as TOPEX/Poseidon and Jason series.
• SSHA - Sea Surface Height Anomalies - Sea surface height with geophysical effects and MSS removed. Geophysical effects removed are from tides, inverse barometer and high frequency wind response.
• SL - Sea Level - Similar to SSH, but typically a blend of multiple instruments, such as tide gauges and satellites. 
• SLA - Anomalies of sea level, similar to SSHA
• Geoid - Earth's gravitational equipotential surface, similar to mean sea surface.
• Dynamic topography - Sea surface height with respect to the geoid.