Hello! Of the default data columns in the Analytics data feed, which
column would show me the source of the visitors? For example, I would
like to know if they came via e-mail, search (Google), social, etc. I
see that some of the values in the page_url column has UTM
parameters--in which case I can refer to the utm_medium. However, I also
see that there is a first_hit_ref_domain that shows additional related
data. Just a little confused on what I should be looking at.