Definition: This is a program that you use to create Web pages. It can be something as simple as the text editor that came with your computer or it can be something that creates the page right in front of you as you point and click away.
If you like to design your pages using HTML then you will probably us a text editor of some sort. They come with a wide variety of options including templates, spell checkers, color coding and much more.
If you don't use HTML, or if you want to create a simple page quickly, then you probrably use something more complex. Editors like FrontPage and Composer are easy to use but don't allow you to add complex things such as JavaScript and DHTML without using their text editor option.
Examples:
I use an HTML based Web site editor to create my Web pages.