It's pretty well described on the CIC website, as below. Basically you get an extra 50 points if you have passed the language requirements and have a foreign degree with an ECA to show that it is equivalent to a Canadian degree or you have at least 1 year of Canadian work experience and a foreign degree with an ECA to show that it is equivalent to a Canadian degree
From CIC Website:
"Education Maximum 50 points
With good/strong official languages proficiency and a post-secondary degree 50
With Canadian work experience and a post-secondary degree 50"
