Speed density uses manifold absolute pressure and an ambient air temp sensor and calculates the density of the air along with throttle position...and gives that value to the computer for fuel and ignition timing/delivery.

Mass air takes a direct value of the incoming air charge and the most common method is the hot wire a wire is set inside the MAF and put into the airflow the wire is then energized..the more air that flows through..the colder the wire gets...and resistance of electricity is directly proportional to the wires temp so the computer knows how much air is flowing based ont he resistance of the wire.

Not so common is the flapper door where the more air that goes through pushes open a flap.

Mitsu..karman vortex in the dsm...some kind of techno voodoo shit that measures the vortices produced by incoming air...black magic.