CPM or Cost Per 1000 Impressions is a metric that represents how much money advertisers are spending to show ads on YouTube.

So narrowing down, CPM is basically the cost an advertiser pays for 1,000 ad impressions wherein an ad impression is counted anytime an ad is displayed.

So, Why CPM rates are important on YouTube?

You get a cut of what advertisers pay when an ad serves on your video. The more an advertiser pays for that ad, the more money you make. Your CPM is a good indicator of how valuable advertisers find your videos and audience for achieving their own business goals.