Can the site owner edit his or her own site and what is a CMS?

Absolutely! In fact, I encourage the owners to participate in adding content on the site. This does take some training. It honestly is not that difficult to learn how to do this if you use a content management system (CMS). What is a CMS you ask?

A content management system is a computer application that allows publishing, editing and modifying content, organizing, deleting as well as maintenance from a central interface. Such systems of content management provide procedures to manage workflow in a collaborative environment. [- Wikipedia]

I predominately use the WordPress CMS with the Avada theme. Other CMSs are Drupal (Open Source), SquareSpace (proprietary), Wix (proprietary), Joomla (Open Source), other Builders (mostly proprietary) that are host specific and on and on.

A proprietary CMS often means the backend is controlled by the company and, once on their system, you can’t move it to another host. They have their own proprietary code. This can make the system safer (security-wise) and more foolproof to use.

Most CMSs these days have many features built-in or, easily added and come with their own themes (aka templates).

Some built-in features you may want are:

• Blog posts
  If you have a blog on your site (always recommended to get good Search Engine Optimization), I can set up a piece of code that will bring the newest post, just the titles or the top 3 posts to, for instance, appear on the home page. You just have to write the post once and the system does the rest.
• Photo gallery
  If you have a lot of photos you want to display of your products or services (such as for: design, architect/builders, artists, storefronts, manufacturers), you can apply multiple categories for each photo and have it display within different galleries, on its own page with descriptions or in pieces on any other page.
• Mobile ready
  You only need to put in your content in once. I set up content to display in the right way for whatever device the visitor is on, cellphones, tablets, small or large desktop computers.
• Calendar