How do emails arrive in Mail that are addressed to a gobbledegook email address?

Some arrive in my Inbox and some in Junk. But my question is, how do they get thru to me when the email address they are sent to bare no resemblance to my email address/es in the slightest?

When I make a typing mistake and send an email to the wrong address, I get a bounce back telling me it can't be delivered. So how do ridiculously addressed emails get thru to me? I thought spam were emails that arrive to Kosher addresses, but this is not what is happening to me. Can anyone please explain?

It would be nice to at least understand how it works.