According to the Longman online dictionary a log is
an official record of events...

The same site defines the web as ...a system of
millions of computers all over the world connected
to the Internet, which allows people to create and
look at websites

A portmanteau word is made by combining the
sound and meaning of two other words, for example
‘edutainment’ combines ‘education’ and
‘entertainment’

When the words web and log are combined into a
portamteau, they create the term "blog" - which
Longman defines as
a web page containing
information or opinions from a particular person or
about a particular subject, to which new information
is added regularly

Blog can be a noun (see above) or a verb.  You will
be blogging!  You are bloggers!