Over the past few years, a big part of convincing new people to jump on board with World of Warcraft has been the Recruit-a-Friend program, which gave both the new and the existing player a bunch of rewards for joining via a referral link. It has brought a large number of new players to the game, but it's going away in early June 2019.
The program gave both players co-op benefits, cool mounts, and even extra game time added to your accounts if the new player sticks around. Blizzard announced that while the program is going away, it will, down the line, be replaced with something new.
Players will have until 11th June 2019 to invite their friends to get in on the MMO, after which your friend will have 90 days to accept your invitation to net you those rewards. You can learn more about the process here.