I have yet to find one, as I am also new to marketo, but this is what I have been able to find thus far:
program- manifests as a collection of child/smart campaigns for a specific purpose and with a specific goal, measured by exisiting lead success or the acquisition of new leads - specific marketing initiatives that hold all of the assets like emails, forms, landing pages, smart campaigns
smart campaign- trigger on one person and perform actions or run a series of actions among a group of people
engagement program- a program that is able to accomlish complex nurturing
child campaign- a special type of smart campaign that only lives within a program or an event
email program- neat setup & dashboard which is built for 1 off emails
Hope that helps!