If you see a forum topic post or reply that interests you or that you like, you can "like" the topic by clicking on the “Like” icon at the bottom of the topic post or reply. This lets the poster know that the topic was helpful. It also contributes to the topic’s popularity, which influences where it is listed in the "Popular" forum tab.
There are also additional reactions available for members to use. Mouseover the "Like" icon to choose one of these options: Love, Clap, Celebrate, Insightful, or Interesting.