Question: I am working on implementation of PLL.

The implementation in MATLAB is done. It should be simulated in a similar way in hardware.
Honestly, I don’t understand what a simulation in hardware means. Does anyone explain it to me?

I have read the software engineers use FPGA for software development. I am familiar with FPGA a lit a bit, like how to describe board in Xilinx, or switch a led on/off…such simple stuff.

Does a simulation in hardware mean to rewrite it for FPGA?

Please, could you give me some example how such code looks like

EDIT 1: PLL will be a part of the receiver. The main my task is simulation a receiver

Answer: 
Simulated in hardware, or simulated as a hardware design? They are different things.

Simulated as a hardware design might mean simulated using a spice type circuit simulator with your loop built out of opamps resistors and caps, and the phase detector done as some suitable implementation of a type I or II detector (generally either flipflops or a mixer of some sort).

Simulated in hardware does not make a lot of sense for a PLL unless you are really doing a discrete time version, where simulating the implementation in something like an FPGA or ASIC might make sense.
Mathworks has a product called HDL CODER toolbox that allows you to translate MATLAB into synthesizeable VHDL which can then be put on an FPGA.

<https://www.mathworks.com/products/hdl-coder.html>

You could try looking into that.