Hardware emulation, the use of special purpose hardware to emulate the behavior of a yet-to-be-built system, with greater speed than pure software emulation.
A computer simulation (or "sim") is an attempt to model a real-life or hypothetical situation on a computer so that it can be studied to see how the system works. By changing variables in the simulation, predictions may be made about the behaviour of the system. It is a tool to virtually investigate the behaviour of the system under study.
模拟：simulation，是抽象出一个物理的或系统的某些行为特征，用另一系统来表示他们的过程并产生结果，倾向于对抽象系统的设计。
仿真：emulation，是在原来的硬件基础上，对现实输入信号的模仿，使系统执行同样的程序，获取同样的结果，倾向于对输入信号的测试。"仿真"的要求比"模拟"高很多，实现起来的难度也相应大很多。
https://www.zhihu.com/question/47732296/answer/107633792