Page rank is a numeric value
that range from 0 to 10 with 10 is the best page rank.
Page rank determines the importance of your page. the
importance of a page determines its ranking in Google search
results.
As the number of inbound important and relevant links to a
page increased its page rank will increase.
When page A links to page B, Google consider that page A
votes for page B.
But Google also analyze the page that casts the vote to see
if it is relative to your page.
So it is not only the number of inbound links, they must
also be important and relative.