The word link in this universe refers to a connection to the Paragangian Community Mind. most Paragangians are linked through a Memory Implant but other people can wear an external link which looks like a metallic round cornered rectangle about one half inch by one inch which can be stuck anywhere on your skin and connects your brain to the community mind. Of course you cannot access as much of the community mind through an external link as through a memory implant, but it's easy to put on and remove you don't have to commit to be a life-long ember of the community and it doesn't remove 3 days of memories as an implant does when first implanted.
external links also now and then get referred to as Temp links
there is one other kind of links, which occurs only once, in my 2012 NaNo Novel , Sen'tran Jenzar rigs up a psuedo implant for Gloria Scott , which is not eligible for a real implant becuase she has not got the dreaming ability/telepathy/shapeshifting genes one must have to receive an implant. But she needs to be able to attend a cerimony one can only attend if implanted.
the way this link works is that she has an external link plus a device through which Jo Jenzar can transmit information which is received through the Community-only part of the implant, translated into a for where Gloria's non-dreamer mind can receive it. there would be some things impossible to transmit, but this enables her to understand the culture well enough to make a mural of their history on the wall of HomeStation. Sen'tran makes it as much like a real implant as he can without causing her to have Exile sickness when it is removed so she does loose three days of memories and regain them when it is removed. The length of time she can use it is limited, and Jo can monitor her thoughts through it but she's usually careful not to abuse that power.