1. In Wechat "emoji" is a superset that also includes memes, where you can use any kind of image as an emoji also add other's emoji to your library (kinda like slack emoji, but bigger and more emphasized). The humor and expressiveness is immense, people use them for daily conversations instead of a quick reaction tool (well that too). Everyone's emoji lib is vastly different and it says a lot about you as a person, it's almost like a personal language.
2. The "Smile" emoji in Wechat actually means hostility [0] in younger generations ("it could mean that you just said something really dumb and the sender doesn’t want to speak to you"). Some older generations folks don't "get" it and still use them for good intent. It's always weird to see your parents send you that.
[0] https://www.scmp.com/abacus/tech/article/3029091/smiley-face...