I appreciate @srhere pointing out that searching should be the first option. I highly encourage it myself. I will still answer this one since the topic title is quite clear and I was unable to quickly find an alternative answer.
In short married and unmarried applicants have different CRS calculations for example under “Core / human capital factors” for a MS degree you get 126 points if you are applying with a spouse and 135 for without. Now if your spouse also has an MS then they can add 10 more points to your score if they also get an ECA done.In this way a spouse can add points to your application and increase your overall score.
Attached below are some threads for further reading.
find an alternative answer.