Under Content > HTML Blocks you will see a list of sections editable through this section. This section is often hidden for clients, but contains the sections listed below in addition to any custom sections for your website.
This section lets you edit, add or delete links in the tertiary navigation of your website. The tertiary navigation is usually found towards the top of your website and includes secondary links that are important, but not enough to be included in the main navigation menu.
Here you can add any content you want to appear under the left hand navigation on your internal pages such as contact information or important links.
This section lets you edit, add or delete links in the footer navigation of your website located towards the bottom of each page.
This section is likely custom to each site and may or may not be used.