Friendversary is the term used by Facebook which means the friendship anniversary or aniversary of being friends on Facebook with a person.
Facebook may decide to create a nice video for you and the friend you are celebrating faceversary with to be shared among your friends, but this is not always happening.
If you are lucky one, you may be notified that Facebook have created the video for you, and you can decide to share it. The video can be found when you access On This Day app on Facebook.
Now to see if you are lucky to have this video, click on the following link to open your ONTHISDAY app, and see what is available for today:
If your video is ready created, you will see it from that page and you can share it with your friends, otherwise, you will just be notified that today you became a friend with someone.