Snapchat has emojis that appear next to friends in your friend list. These change over time based on how you interact with that friend. This is what each emoji means. These are private, and can only be seen by you!
Update: May 2108. Some friend list emojis have disappeared. Read more.
Here is the full list of friend list emoji meanings on Snapchat from Emojipedia.
Snapchat Friend List Emojis
See also: every emoji in the Trophy Case or the verified account emojis.