using a countif function nested within a sumproduct function

I have a formula which is a countif function nested within a sumproduct which counts the number of threatened species from a list occurring in a particular cell.

The fomula is =SUMPRODUCT(COUNTIF(B2,"*"&$G$2:$G$9&"*"))

where G2 to G9 is the list of threatened species.
Column B contains the site's information which mentions what species are present at each site.

What I would like to know is how does this formula work?

Cheers