DEFINITIONS & EXPLANATIONS (wikipedia)

MILD ASSIST HYBRID (MicroHybrid; Power Assist Hybrids) are essentially conventional vehicles with some degree of hybrid hardware, .. with start-stop only or possibly in combination with modest levels of engine assist or regenerative braking features. Cannot provide all-electric propulsion.

FULL HYBRID: (strong hybrid)... runs on engine, or batteries, or both.

Synergy Hybrid Drive (Toyota brand name)

• "drive-by-wire" for gas pedal and gearshift lever

• Continuously Variable Transmission maintains optimum engine speed & torque (~1500-2000 RPM)

• engine is downsized to average load on the car. Battery provides additional peak power

• engine turns off at stops

REGENERATIVE BRAKING: recharge battery while braking

ADVANTAGES OF ATKINSON CYCLE ENGINE

versus the normal Otto cycle

• minimize engine drag via an offset crankshaft to minimize piston drag

• longer power stroke recovers more energy;

• the unique intake prevents drag caused by manifold vacuum

DISADVANTAGES OF ATKINSON CYCLE:

• much reduced torque, particularly at low speed
  (compensated by battery assist)

• compresses less intake air (often compensated by a supercharger to increase intake air -... known as Miller cycle engine)