This is an excellent overview of ImportXML function with detailed examples in 9 short chapters.
Chapter 3 - Why should I care about using ImportXML?
We can now look at a page, decide what information we want by looking in the source code, finding the HTML element and by using Xpath we can dig it out.
ImportXML is how we’re going to pull it in. ... Instead of copying and pasting information from a bunch of websites, this is will do it in 2.2 seconds. It automatically pulls it into a spreasheet so you can work with your data however you want.
If you’re a trader, you can automatically pull in all your stocks into one spreadsheet effortlessly. If you’re an SEO, you can acquire 100’s of link targets from around the web. If you’re an online retailer, check up on your competitor’s pricing for Product XYZ as soon as it changes!
Chapter 4 - Your first ImportXML lesson ...