Wiki alternative URL's

I've noticed that there seems to be more than one landing page for a Wiki - i'm not sure what the true differences are.

I created two wikis in the root, let's call them wikiA and wikiB, can someone explain what these URL's should show, and why they appear to be duplicate?

1. /w/wikiA or /w/wikiA/default.aspx - same page, but I have no problem with this. I use canonical tag to fix this.
2. /w/wikiA/defaultwikipage.aspx - what is this? the content is similar but different. This URL is linked to from one of the widgets I believe.
3. /w/ - on the face of it I expected this to show some content from both wikis, but it doesn't. it shows wikiA content, but with a widget showing Revisions at the bottom
4. /w/wiki/ - this version works on staging, but not my local copy. I assume I'm missing some folder and default.aspx, but it wasn't immediately obvious where.

Before I start to dig in deeper into these, can anyone give me an overview which of these should exist when the content is largely identical. Perhaps they are targeted at different users, but it appears that they aren't just for registered users..