Non-tidal Sea Level: NTSL, as the name suggests, is sea level minus the tide. It includes the wind and pressure-driven changes of sea level as well as many other (non-tidal) causes of variation such as El Nino and ocean eddies.
Non-tidal Sea Level Anomaly: NTSLA is the anomaly of NTSL (with the long-term mean subtracted). See the Adjusted Sea Level info button for details.
Terminology: Non-tidal Sea Level Anomaly is sometimes referred to as either 'tidal residual' or 'non-tidal residual'. Both (confusingly) refer to the signal left over once a tidal prediction or analysis, which usually includes the mean, is subtracted.