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: 
A PLL is sufficiently straightforward and analogue that simulating it in hardware doesn't make much sense. Just go ahead and build it, and see how it behaves.

There might be a case for simulation if you couldn't get hold of some of the components, but still wanted to have a hardware model of the loop to integrate into something else. Say you couldn't get some microwave VCO and PSD yet, so built something round a 4046 with the same bandwidth and loop filters.

Another case might be to simulate the VCO's frequency to phase response as an integrator, so that you could build the loop and loop filters, and see how they responded with the ability to probe 'phase' (the integrator output voltage representing phase) directly on an oscilloscope.
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.