If you like a post, it's nice to reward the person who made it! If you look at the bottom right corner of that post you have a 'Like' button. Click this button , and your 'Like' is recorded underneath that post Also once clicked the original poster receives an alert to notify them of the 'Like'. You can also see all of your 'Likes' through your profile page. In this way it's easy to see which posts in a thread have been useful, or have helped resolve an issue and so on. Likes also contribute to the original posters trophy count, and help establish and build their reputation on the forum.