Ocentric vs Ographic latitudes

Latitude and longitude points are used to specify a location on the surface of a planetary body. The latitude measurements can differ when using a sphere (geocentric) or an ellipsoid (geodetic) model. Geocentric latitudes are calculated using the angle that is created from the center of the earth and the equatorial plane to the perspective point. Geodetic latitudes are calculated by using the angle created from the equatorial plane and a perpendicular line of the perspective point. While Earth datums can use a geocentric spheroid model, Earth datums more commonly use the geodetic latitudes in an ellipsoid model.

    

For more information:

Image one is from Encyclopaedia Britannica, Inc, https://www.britannica.com/science/latitude

Image two is from Proj, https://proj.org/operations/conversions/geoc.html