Cache busting is telling the browser to refetch assets because they have changed, caching assets allows the browser to retain a file "in memory" without having to download it each time it visits your website, making the page load faster, however if you have done some changes to the styling or logic in your JS, you want to "bust the cache" so the browser gets the new updated files.

I've recently experimented with the awesome plugin "Blitz", which is a full page caching plugin for Craft CMS that generates static HTML files of your pages, so you can serve them ultra-fast using Nginx or Apache.

Hubspot is a marketing automation suite of tool that allows marketers to create landing pages, blog posts, hosted lead forms, and also comes with a CRM system, when a company is already using Hubspot to power their content marketing, but are looking to refresh their website, they might want to integrate the existing content from their HubSpot portal into their new website, we at Guilty encountered this with one of our latest project, and thought we might as well build a plugin for this that can be used by our self and others in the future to make this task a bit easier.