I can only imagine it's a term inheritted from fly by wire aircraft i.e. syncros used to feedback positional information to onboard asic processor computathingamybobs in order to steer the boat through electrical means rather than mechanical... probably completely off the mark but that'd be my guess without employing the use of Mr Google
It almost certainly refers to the throttles. With the more modern engines (and indeed some of the olr ones where they have been retrofitted) the throttle lever is just a potentiometer which operates an electic/solenoid activated throttle on the engine.
Volvo have used this system since the late 90s as do other manufacturers.
It basically means something is controlled my electrical means rather than mechanical or hydraulic means. Usually throttles or steering. Controller is a potentiometer instead of a cable or pipework etc.
It means that they can replace expensive to make and maintain cables and pulley's to move throttles and gears with electric wires and a chip or two and then double the price to you.
I still cannot believe that Mailspeed Marine has an LED nav light in their latest catalogue for £575.99
I was to understand that LED's are cheap. Maplin sells a single superbright bright green LED for £1.59 and red one for £1.79.
Put a few of them in a housing and its close to 600 quid.