Yes, my question may seem odd, but often in Google I see the site's own pages showing up as backlinks.

So my question is basically does google count your own site's pages as backlinks (with bonuses to whatever page is linked to most) AND give you a seperate boost for having more pages in your site?

In which case, it would probably be better to just build a massive site then a decent one with lots of links to it? Or not?

And what's a good relevancy of links perecentage? Like 90% relevant? Or is 100% actually better? natural is better right? In which case can having more pages in your site give you more backlinks which are on-topic and therefore increase relevancy?

Thanks in advance

No it does not. It only counts linking from other sites, not its own.

Linking to yourself to the best of my knowledge provides no enhancement in serp ranking. You must get backlinks to other sites and if they are relevant to your content it helps so 100% backlinks with content related material is your best option. Now it is still better to have some backlinks with no content relation then know backlinks at all.

Thanks, but I'm pretty sure I've seen sites' internal pages show up in the "link:http://www.mysite.com" query on google.

Oh but also, maybe that could just be subdomains on the same webhosting?

Subdomains linking to each other than the main domain would count as backlinks? Right?

Thanks, but I'm pretty sure I've seen sites' internal pages show up in the "link:http://www.mysite.com" query on google.
It might be a glicht or something.

Backlink is backlink, from other websites.

Subdomains, folders, deep files, are not backlinks, they are in-between-links.

Normally, not always, backlinks are more precious than in-between-links according to Google's eyes. Sometimes, a good in-between-link is more precious than backlink. You just need to test it out.

I've read it also that for a backlink to be considered a valid backlink, it should be from different C block server. So, you couldn't buy several accounts of web hosting, built one hundred sites, link them to one website (even with no cross linking), and consider them as backlinks. Google is smart enough to figure that out. In fact, some websites are delisted because of this.

So, no, your own page (subdoms, folders, etc) is not considered as backlink.