The Web Link field references an external web resource such as a web page, pdf document, Youtube / Vimeo video, image, or any other public URL. The Web Link URL source can be hard-coded in the field settings in the portal as a “Static Web Link” or can be set up as a "Dynamic Link" that pulls field data in the form to populate the link. The Dynamic Link will allow for use cases such as Lookup Data that drives a product image or referencing computed fields for dynamically generating a URL source.
"Static Web Link"
"Dynamic Web Link"