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Terms defined:

D-Jet = short for Druck-Jetronic (druck is pressure in German). The first mass-production electronic fuel injection system, devised by Bosch, and used from the late 60s on VW, Mercedes, Volvo, and Porsche cars, until the mid-70s. D-Jet is a speed-density system (see below).

L-Jet = short for Luft-Jetronic (luft is German for air). The second mass-production electronic fuel injection system, also from Bosch. L-Jet is a mass flow system (see below). The usual L-Jet sensor is a flapper type valve that measures airflow mechanically. Later systems used a "hot-wire" sensor that measured air using an electrically heated wire in the airstream, using the cooling effect of the air.

MPS = manifold pressure sensor, key part of the D-Jet system. This is an electro-mechanical system with a metal diagphram and two coils to provide inductive signals to the ECU. See speed/density and MAP.

speed/density EFI = a method of fuel injection that uses engine speed as one signal, and manifold pressure and air intake temperature as paired signals to derive air density and engine load. see MAP.

mass flow EFI = a method of fuel injection that uses the mass of the air flowing into the engine as the primary signal. Theoretically, this is all that needs to be known to derive mixture (and thus calculate fuel). In practice, you also need to compensate for cold-running conditions.

MAP = manifold absolute pressure. Can be expressed in several units of pressure, but is most commonly quoted in kilo pascals (kPa). 0kPa is absolute vacuum, 100kPa is (more or less) normal atmospheric pressure at sea-level. MAP is measured in the intake manifold between the throttle(s) and the intake valve(s). Typically, you'll see MAP values between 20kPa (deceleration) and 98kPa (WOT on a good engine). Idle is usually around 35-40kPa.