Check out example codes for "fetch mobile speed and desktop speed score from google insights". It will help you in understanding the concepts better.

Code Example 1

You can return all possible audit categories using the following example:

1. URL: https://www.google.com/
2. Return-Fields: lighthouseResult/categories/*/score
	* is a wildcard
3. Indentations (PrettyPrint): no
4. Strategy: Desktop
5. Categories: Performance | Progressive Web App (PWA) | Best practices |
				Accessibility | SEO
6. Api-Key: {YOUR_API_KEY}

https://www.googleapis.com/pagespeedonline/v5/runPagespeed?url=https%3A%2F%2Fstackoverflow.com%2F&fields=lighthouseResult%2Fcategories%2F*%2Fscore&prettyPrint=false&strategy=desktop&category=performance&category=pwa&category=best-practices&category=accessibility&category=seo&key={YOUR_API_KEY}

And the JSON-Response looks like this:
{
    "lighthouseResult": {
        "categories": {
            "performance": {
                "score":0.99
            },
            "accessibility": {
                "score":0.7
            },
            "best-practices": {
                "score":0.77
            },
            "seo": {
                "score":0.9
            },
            "pwa": {
                "score":0.56
            }
        }
    }
}

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