"If you start d4, your goal is an e4 break. If you start e4, the goal is a d4 break." Why?
I watched a YouTube video that said studying openings is completely overrated if you're under 1800 rating. One principle it stated was, if you start d4 then you should try to set up an e4 break, or if you start e4 then try to get a d4 break. And you should play the break when you can do so without losing material.
Obviously it's situational and there are exceptions, but it got me curious -- why is a central pawn generally better for white (who gets to do it first), even if the material ends up even? I've watched enough commentary of chess candidates and analysis of grandmaster games over the years to have seen this be a real theme, but I don't actually understand why. If the material remains even before and after the break, what did it achieve?