There are three types of links you can create in Pressbooks:
Links are created directly in the editor. First, either place your cursor where you want the link to appear, or highlight the text that you want to turn into a hyperlink. Then, select the link icon in the toolbar. This will launch a small pop up under where the link will appear.
Paste the target URL into the box and select the blue "Apply" button. If you want more control over how the link behaves, you can alter link settings by selecting the gear icon.
The search function is for internal links, and will be discussed below.
You can insert internal links that will take readers to other parts of your book. These links can be for chapters, parts, front or back matter. You can also link to specific points by creating anchors in your text. Anchors must be uniquely named, and are helpful if you want to direct readers to a particular image, section, or concept.
Internal links follow a regular format. For large items, such as parts or chapters, the internal link is everything that comes after the .com portion of your URL. For example: /chapter/[chapter-title-here] or /part/[part-title-here].
For anchors, you will include the chapter or part, followed by /#[anchor name]. When put together, an internal link to an anchor would look something like this: /chapter/introduction/#imageone.
When you insert a link (as described above), you will have the option to search. This will allow you to search for any preset internal link in the book rather than typing it in manually.
The best practice for anchors and internal links depends on what content you are linking to, and how you want it to appear to your reader. For a detailed step-by-step, see the "How To" file in the Resources box.