Your staging site looks great, all links are working! Then you launch the site to the live URL and all the links break. This is the number one problem clients get into if links are not created properly on the staging site.
Linking internally (versus externally) means linking to pages you have created within your site.
Highlight the text you want to link and click the link icon.
Type the name, or part of the name, into the Link field.
As you type you will be presented pages whose title matches your entry.
Select the page to which you want to link.
NOTE: [Optional] You can also enter in a title at the same time. This is hover text that displays when a mouse hovers over the link.
IMPORTANT: You MUST select the page from the suggested pages and DO NOT type in URL of the page. This leads to errors! If you do this on your staging site, THE LINKS WILL BREAK when the site launches.