This has recently been brought up that we should improve this off-topic/close reason.
While we can agree that this VTC reason is less than ideal (perhaps too broad, should be two separate reasons) right now in Beta we are limited to 3 pre-defined off-topic reasons.
The full reason (emphasis mine):
Questions must involve real code that you own or maintain. Pseudocode, hypothetical code, or stub code should be replaced by a concrete example. Questions seeking an explanation of someone else's code are also off-topic.
@chillworld brought up in chat that
Maybe we should change "Questions seeking an explanation of someone else's code are also off-topic." to "Questions seeking an explanation of code are also off-topic."
As a matter of example, it's conceivable that any of us go back to code we've written months or years ago, and not understand our own code quite clearly because it's not well documented or well-written.
Some mentioned that this question might be a duplicate of this one (and I can understand the sentiment) since this specific wording practically started a flaming/trolling war between CR regulars and a regular on MSE (as well as a new user) I think it might be wise to revisit this.