waste spark is very easy to understand - imagine it as the spark plug will fire anytime a piston reaches TDC - just like your motorcycle.
in any even no. cyl engine cylinders are paired together at the crank, a regular straight 4 engine has cylinders 1-4 and cylinders 2-3 as mechanical companions - meaning that if cyl 1 piston is at top - so is cyl 4 - however one will be at ignition phase and one cylinder will be at exhaust phase (hence the term waste spark - the spark is wasted as it did not make ignition happen)
its easier to write into the ECU because you only need 2 drivers to switch the coils on and off, rather than 4 - in a distributor ignition there is 1 coil for all cylinders, - the problem makers face with that is that it does not get enough dwell time to charge up at higher rpm - hence the introduction of multiple coils.
due to the nature of this system - the spark plugs where opposite to each other - meaning on one plug the centre electrode will wear down and the other will wear down its side electrode - it also mandates that there is no current leak anywhere and that the plug gaps are correct and both plugs are 100% similar - otherwise it will misfire.