Responsiveness, when it comes to websites, is a websites ability to adapt its appearance to difference screen sizes and shapes. We have all been on a site on our phone and had to zoom in and out to view parts of the page. It isn't fun and you shouldn't need to put your visitors through that. All the sites that I build are custom designed and built to look and work great on any device you use.
The Content Editor, is the difference between you needing to email or call your website designer to make and update, and you hopping on your laptop and updating almost anything on your site in seconds. Using the Content Editor is easy and noninvasive to the design that I have built on the site. This gives you the freedom to control your site, because, well it is your site after all.
In short the CMS or Content Management System, is your access to a easy to use database. If you are publishing blogs, updating products, changing your team members page, this can all be quickly done from the CMS system. No more needing to update individual pages. The CMS does it for you.
Web animation, is whatever you want it to be! You could have a button change colour or a video play on the page load, or a eagle fly across the screen when you click a link. Whatever you would like, it can be done. Animations make websites magical.