Why do you need the Editor Advanced Link module? Mainly because it provides a lot more information to your links that helps with SEO than simply adding a link on it's own.
Here's what the link interface looks like this with a base Drupal installation:

After installing the Editor Advanced Link module, the link interface looks like this:

And if you expand the ADVANCED section, you'll see this:

You'll notice several additional fields have been added to the dialog box:
- TItle. The text in this field will pop up when the link is rolled over and provides additional information about the page being linked to.
- ARIA label. This is very useful when the link text is not descriptive. For example, if the link is around an image or button.
- CSS classes. You can add specific CSS classes that are used on your website. Note: you cannot put actual CSS style syntax in this field.
- ID. Allows linking to this content by using a URL fragment (e.g., <path>/<page-name>#here).
- Open in new window/tab. When clicked, the link will open a new tab or window rather than in the current window.
- Relation (rel). This attribute specifies the relationship between the current page/document and linked document/resource. (e.g., "nofollow", "follow", "stylesheet", etc.).
We also use the Editor File upload and CKEditor Entity Link modules on our Drupal installation to help editors with on page linking.
For additional information on installing and configuring the Editor Advanced Link module, head on over to our Drupal SEO Guide. If you don't have time to do it yourself, let Volacci take care of your Drupal website's SEO for you.