golfmiketango wrote:But, since it's an open-access wiki, OP could correct the problem himself, if he so chose? Or I'm mistaken?
The Factorio Guide is not a Wiki, and it's not open-access, it's read-only in HTML format, so the OP can't correct that,
Ah, well then I stand corrected. OP, I suppose I should have mentioned that your best bet, either way, to understand things like this, is to play with them yourself in the game. If you aren't yet producing a torrent of "plates" to play with in-game, then you might try the "Creative Mode"
Mod which can be installed via the mods menu of the game. By using the several cheats it has to offer almost anything you might want to try can be given a go.
The "short answer" to your question, however, is that, in the situation shown, the plates have reached the end of the belt and are piling up as they have nowhere else to go. After a while this behavior starts to look so normal that it's hard for an experienced player to think of it as in any way confusing -- but I am pretty sure I remember looking at that very diagram on my first or second day of factorio and thinking "so what the @$&^#%$ is going on in that picture?"
Although this is not the point of the picture, by the way, probably the most powerful -- but, sometimes, also the most annoying -- feature of splitters is that when output lanes "jam" in this way, and the "jam" extends all the way back to the splitter, the splitter will automatically change its behavior, to output /all/ items input on the same lane (i.e., left- or right-hand side of the belt) onto the corresponding non-jammed output lane. (That's a dense bit of words, there, you may have to read it a few times before it clicks... or, like I said, just try it, the game is worth a giga-word and then some). So a splitter will "never" (well, not strictly true, but close enough) impede the flow of items from A to B due to a problem with some unrelated input or output "C".