Hi Mandy,
Triggers are active, so anytime someone does a certain action (click, register, etc) then something happens (your flow step). Filters help to narrow down what you're looking for (ex: you can use a click link trigger but filter only on leads with "hr" in their job titles).
Here is a good article on triggers and filters:
http://community.marketo.com/MarketoArticle?id=kA050000000KzKACA0
As for scoring you'd need triggers so they can score based on an action someone is taking. If you make different scoring smart campaigns and activate them, they will run all the time so you don't need to creat duplicates. (On scoring:
http://community.marketo.com/MarketoArticle?id=kA050000000L7cJCAS)