MODX will automatically generate URLs for internal links to other MODX resources using the URL tags - [[~42]]. The resource ID of the resource for which you want to create a URL is the required property. You can use a TV, snippet, or any other method of outputting a resource ID into the link tag, as long as it produces a valid resource ID.
But sometimes just plain URLs aren't enough. What about passing key-value pairs in a query string? What about named anchors? What about switching to HTTPS for something like a secure login page?
These recipes will help with solutions to these and other questions relating to links and URLs.
Use Revo's slick drag-and-drop capabilities to drag a resource from the Tree and drop it in the field of the resource you are editing to get a MODX link tag for the dragged resource inserted into the content.