This is the 225th most frequent German word.
außerdem
"Besides" or "in addition."
"außerdem" is used to emphasize another issue linked to the first one.
Sie hat keine Hausaufgaben gemacht, außerdem kam sie zu spät zur Schule.
She didn't do her homework; furthermore, she was late to school.
"außerdem" is used to connect two positive outcomes or events.
Wir haben nicht nur viel gelernt, sondern uns außerdem gut amüsiert.
Not only did we learn a lot, but we also had a good time.
"außerdem" is used to introduce an additional piece of information.