Fluid linkage in the torque converter.

What does that mean?

In an automatic transmission there may not be a direct linkage with the engine, to the gearbox.
It might be depending on the design, connected through liquid.

One side spins the liquid(connected to the engine) and the other side gets spun around by the liquid.
This can be changed by moving the distance, but even when farther away, there is still a little bit of momentum transferred between the liquid.
Think like having two blenders with one upside down on the other, and powering the other one by turning on one.

There can be direct links which are better for gas mileage but change the dynamics of the car, but that’s getting a bit beyond the general overview.