A permalink provides you with a link to the exact view of the map you are currently looking at. You can then share this link with others to let them see exactly what you see.
To add a permalink control to your map you need to define where the user will click to show the permalink panel. In this example, we use an empty anchor tag.
You must also define the location and dimensions of the permalink panel that will appear, and pass them as a parameter to the Permalink control. You can also give it a title.
There are several other options you can set as well - consult the documentation for a full list.
When you've set up your permalink the way you want it, add the permalink control to the map.