What is the meaning of XT in computer?

Excuse me, but could you possibly explain the significance of the term 'XT' when it's used in the context of computers? I've noticed it in a few places and it seems to hold some specific importance, but I'm unsure exactly what it stands for or represents. Is it related to a certain type of hardware, software, or perhaps a programming language? Any clarification you could provide would be greatly appreciated.