The major player in the blog game is WordPress, a content management system (CMS) that powers millions of websites, including The New York Times, Quartz, and Variety. WordPress-powered sites are incredibly easy to set up, customize, and update—ideally on a daily basis. You aren't required to learn fancy-schmancy FTP tricks (though you can certainly use them if you like), and there are ridiculous numbers of free and paid WordPress themes and WordPress plug-ins to give your website a pretty face and vastly expanded functionality. Though WordPress dominates the blogging space, it isn't the only blogging CMS of note, however.
PC and Mac website software used to be very popular – maybe you can even remember Microsoft Frontpage or Macromedia Dreamweaver, as it used to be called. The advantage of such programs is that you typically pay (a larger amount) upfront and can build as many websites as you like. The downside is that you need to take care of hosting your website yourself, which incurs additional costs.
Responsive design is a popular web design strategy used by some of these site builders. This approach reformats the same webpage content to fit different screens. But in terms of SEO (search engine optimization), the search engines only care about whether a site displays suitably on mobile screen sizes. Both Bing and Google have pages where you can enter your URL to see if your site plays on mobile acceptably.
Even if your site’s primary purpose is not to function as a blog, you may find yourself requiring one at some point (Be sure to read the how to start a blog guide for a complete overview), either to keep your visitors updated or to use as a marketing tool. SEO, for example, is something that requires the creation of content to get your website noticed by search engines. Most website builders have built-in content management systems that allow you to write and edit blog posts in your browser. These systems make it easy to create rich content on the fly.
While the the best of them offer surprising amounts of flexibility, they also impose stringent enough restrictions to page design that you shouldn't be able to create a really bad looking site using one of these services. Typically you can get a Mysite.servicename.com style-url with no commerce abilities for free from one of these services; you have to pay extra for a better URL and the ability to sell. One issue to consider is that if you eventually outgrow one of these services, it can be hard to export your site to a full scale advanced web hosting like Dreamhost or Hostgator. If you know that's where you are eventually going, it may be better to skip the sitebuilder step.