DCTs (DSG) technology has gained a substantial market share in the recent times ( up from 3.4% to 8.5% market share in the last 5 years). This video illustrates with the help of animation why DCTs are the best transmission ever.
A dual-clutch transmission (DCT) is an automated automotive transmission, closely related to a manual transmission.It uses two separate clutches for odd and even gear sets. This video also gives a brief introduction on working and drawbacks of a regular manual transmission.//Learn Engineering
It can fundamentally be described as two separate manual transmissions with their respective clutches contained within one housing, and working as one unit.
Although usually operated in a fully automatic mode, many also have the ability to allow the driver to manually shift gears in semi-automatic mode, albeit still using the transmission’s electrohydraulics.