The difference between "average" and "expectation"

[qxx-alvin]

Hi maelfabien, I have a question about your article Graph Analysis. For Erdos-Rényi model, you mentioned that

The average degree is given by n×p.

and

The degree expectation is given by (n−1)×p

I know that for binomial distribution in the article, the expectation is (n-1)×p. But what does the "average degree" mean? I am puzzled about these two concepts. Could you please explain it? Thanks in advance.