Having run this website, or a Canadian version of it, for a number of years I have done much research into menus systems for websites. Having seen what has been available when you use a CMS I was less than impressed. I had always thought there was a simpler easier way.
I think I can say that the majority of menus are variations of the html unordered list ul and li tags. CSS s typically used to make these list appear on the page in the manner the designer desired. I have also seen some pretty scary menu implementations, these are often the product of companies such as Microsoft and Adobe.
What my menu system evolved into
The menu you see on this website is the result of many years of me playing around with many options.
I thought that I had a pretty good working menu that I called the "side" menu. However, when Google introduced its "Mobile-Fiendly" Test my website pages failed. I had to rethink my design.
My menu phylosophy
Basically, the KISS principle. An example of a non-simple approach. Too many menu options on a page that scales for Responsivity. Menus and images need to be scaled appropriately. A page that has too many menu options is always going to difficult to render on a Smartphone. Either you change the menu completely, as did the EssexInfo Responsive theme, or you change the menu display as I do using @media queries.
If you view the example I link above on a Smartphone you wiil see little else than a very crowded menu. Even if you manage to find the menu option that you are looking for you will not see the content on the page, just the menu again!
Links to other resourses for webpage menus