Emoji are ideograms and smileys used in electronic messages and Web pages. Emoji are used much like emoticons and exist in various genres, including facial expressions, common objects, places and types of weather, and animals" (Wikipedia).
In June 2016, Facebook changed their emoji game to better represent its diverse user-base with your choice or skin tone and gender (all of which appear in the messaging app once it’s been updated with the most recent patch). It's easy for people who use Facebook app in smartphone to choose the emoji, but it's not easy for web-browsers-users. Some common emoji can be typed, however, the others is for Facebook app only.
But now, you can copy and paste every Facebook emoji to Facebook chat windows, comment section, status... with emoji facebook. By clicking the emoji, the emoji is copied to clipboard, and you can paste the emoji anywhere your want. It's fast and easy.