A website builder is a web application that can use to create web pages easily without any manual code editing of any language related to web development technologies. An HTML editor and website design software or web development application is also called as an off-line web builder, that's why there have two kinds of website builders. The first kind is the online website builders an online proprietary tool that provided by web hosting companies, and the second is the off-line web builders a software which runs on a computer to create pages off-line and which can then upload and publish these pages on any web host. The online website builders are popularly and often called as a website builder than the HTML editors. Therefore, if someone tells you about web builder, just refer it to the online web builders and not to the HTML editors which has its own title.
Website builders are (too) different from web hosting services, they are online tools for web developers which often provided by web hosting companies. Actually, if a web builder is not yet installed on a web host, it is a software in the beginning which is needed to be installed on a host to be an online tool that can be use for building a website. A software of web builder has an own software developer, but some web hosts developed their own online builder instead of providing the builder that they've not develop. Many web builders have both HTML and object tools. HTML tools are divided into those that have a text mode which allow manual text editing of the HTML source code and those that only have a WYSIWYG (what you get is what you see) mode. The object mode allow the web developers to manage the objects or gadgets on their site, such as the header's image, title, and slogan, the news on the sidebar, and the content on the footer.
Many of the website builders that provided by web hosting companies, on the Internet, have a WYSIWYG mode on their HTML tools, and that mode often has its partner, the text mode that allow the user to edit the HTML source code of the content that the WYSIWYG mode have made. There's also an object mode where you can manage the objects of your site, for example you want to change the logo on the header of your site, you will need to go to the header's object and edit the logo, you can do that because the builder often have an object mode. That mode is also a part of a WYSIWYG web builder, but it doesn't mean that a WYSIWYG mode and an object mode are both the same. Most object modes of web builders have a drag and drop interface where you can add, remove, and edit gadgets, and rearrange these gadgets on your site by just a “click and drag”. WYSIWYG website builders are online tools with a sure WYSIWYG mode on HTML tools for creating web pages, and because that builder specify a kind of builders, means that there's a website builder without a WYSIWYG mode.
Some web hosting providers with a site builder introduce their features as easy website building tools with a drag and drop interface which is easy-to-use that can build a website in just minutes. Just remember that a website builder is different from web hosting service, and it is often refer to online website builders than to the off-line web builders which has their own title, that called HTML editors.