Hi Evelyn,
There are a handful of articles Marketo publishes that may be helpful for you. Try selecting the "University" tab at the top, or check out these pages:
-
Smart List Filters-
Miscellaneous Concepts-
Programs & EventsBut to answer your example question, the engagement engine refers to engagement programs - specifically, an easier, more automated way of pushing people through nurture paths. Smart campaigns can be anything that makes something happen - send an email, change a data value, etc - and are the little lightbulbs in your Marketing Activities area.