Can someone please explain to me how this works? i keep hearing about it but don't have a clue what it is.

这是美国的一种一拖二的电感镇流器的启动模式，灯管启动顺序有先后，一般情况下超前侧（有电容）灯管启动完成后，滞后侧（无电容）灯管才会后启动。

Here's a diagram of how it works, and I'll try to explain it to the best of my understanding:



So in the diagram you can see one of the lamps is in series with a capacitor while the other isn't. I believe the capacitor makes it so that one lamp's strobing is slightly behind the other, hence where the term "lag" comes from. From what I have found based on some research, the reason for this is that it reduces the overall noticeable 120hz strobe of the two lamps, compared to if they were both in perfect sync.