Web scraping is a method of automatically gathering data from websites in a structured manner and storing it into a local database or spreadsheet. Why would you do this? Because you're lazy. Or because it's really impossible to copy-paste all the data you need from the website.
Some popular use-cases of web scraping are price comparison sites of products from different companies, lead generation from collected contact information, trend analysis of popular topics in a certain location. I simply wanted to see what are the most popular movies of 2018 and what features they have.