TX: Tencent is the most representative of TX in daily life. Sometimes "classmates" also use TX, flirting, vomiting blood, playing truant, provoking, exploring the world, surrendering, sighing, staying up late, talking, tinea corporis ... all of them are very popular.

XD is an expression, you should look at it horizontally. XD is a malicious smile.

YD； Er, it probably means lewd:)