In my dictionary the definition of a hub is:
Centre of activity, attraction or attention. It also says it’s a synonym of focal point. And what is a focal point? A joint at which rays (light, heat or sound) convert to diverge.
Maybe it’s not so easy to understand but let’s give an example:
a big airport is usually called a HUB. Why? Because planes come and go , it’s a centre of activity where planes converge(arrive , land) to diverge(leave, take off). Now it’s clear what a hub is? I hope so.
So let’s bring this new definition to our world of internet and websites. When a website could be defined an Hub? When it’s a link magnet in one way and a link container in the other way.
In conclusion an HUB is a website that has a lot of incoming links and a lot of outgoing links.
Again in my dictionary it defines an authority: ”a citation ( as from a book or file) used in defence or support: the source from which the citation is drawn”.
To give you an example my dictionary where I’m taking this definition from is an authority.
Now what’s the idea? If a lot of people take my dictionary and bring citations declaring, as I’m doing here, where they came from this authority becomes very AUTHORITATIVE.
And what means authoritative? Again in my dictionary: “entitled to credit and acceptance”.
Now, going back to our websites world what does it all mean? It means that a website with a lot of incoming links is an authority because it is cited by many other websites. And if it is an authority for a lot of websites it becomes very authoritative.
And here comes the idea behind the Google algorithm. A powerful website owes a good search engine ranking position not only for its content but also for its authority.