Source: https://blogs.umass.edu/p139eck/2012/10/24/types-of-hybrid-vehicles/
Summary of Hybrid Variants
Feature
Mild Plug-In Hybrid
Hybrid Hybrid
Electric Motor Only N/A Yes No
Engine Only N/A Yes No
48V Hybrid System Yes No N0
External Charging No Yes No
Cost Lower Higher Medium
What differentiates a mild hybrid from any other hybrid type, is the lack of direct
connectivity to the vehicle’s transmission. Mild hybrids only support the vehicles
engine by monitoring and offloading the electrical power demands.
Manufactures still want to squeeze even more efficiency out of the internal
combustion engine. It’s a far cheaper way on improving emission without
compromising on performance.
References
https://www.volvocars.com/uk/about/human-innovation/electrification/mild-hybrids
https://www.caradvice.com.au/279850/hybrids-explained-mild-v-full-v-plug-in-v-extendedrange-electric-vehicle/
https://practicalmotoring.com.au/car-advice/what-is-48-volt-mild-hybrid-technology/