What's the difference between cart abandonment rate and checkout abandonment rate?

I've been diving deep into my store analytics lately, and I'm getting confused about these two metrics that everyone keeps talking about. My Shopify dashboard shows different numbers for cart abandonment and checkout abandonment, and honestly, I'm not sure which one I should be more worried about. Last month, I noticed that about 70% of people who add items to their cart don't complete a purchase, but then I see another stat saying only 20% abandon at checkout. That's a huge gap, and I'm scratching my head trying to understand what's happening in between. Are these people just window shopping? Did they get sticker shock when they saw shipping costs? Or maybe they're comparing prices with competitors? I'm spending a fortune on Facebook ads to drive traffic, and seeing all these abandoned carts is killing my ROAS. I need to understand exactly where people are dropping off in my funnel so I can fix the right problem. Some of my merchant friends tell me to focus on checkout abandonment because those shoppers are more serious, while others say cart abandonment is where the real opportunity lies. I'm tired of guessing and throwing random solutions at the wall. I need to know the real difference between these metrics so I can implement the right strategies and stop leaving money on the table.