You can "Like" an activity to show your interest and support to that activity.
Liking an activity
Click under the activity you like. When you like an activity, the "Like" button will be highlighted to show that you already click "Like" on that activity. The activity displays the information of like numbers or people who also like the activity right below it. If many people have liked the activity, you can click to expand the view to see other "likers".
Unliking an activity
To unlike a "Liked" activity, simply click .