How does Mathf.Clamp work in this scenario?

There isn’t really any problem with this code but I want to know how this works. I can’t wrap my head around it. what is rb.position.x/rb.position.z and boundary. for?
I was following the space shooter tutorial up on Unity and I was confused about it. So I followed the docs but the docs made no sense either.
Thanks for reading this!

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

[System.Serializable]
public class Boundary
{public float xMin, xMax, zMin, zMax;
}

public class Boundary : MonoBehaviour
{
public Boundary boundary;
public float tilt;

void Start()
{
    rb = GetComponent<Rigidbody>();
}

void FixedUpdate()
{
    rb.position = new Vector3
    (
        Mathf.Clamp(rb.position.x, boundary.xMin, boundary.xMax),
        0.0f,
        Mathf.Clamp(rb.position.z, boundary.zMin, boundary.zMax)
    );
}

}

So what Mathf.Clamp does:

  1. It takes 3 parameters: your float (rb.position.x), min value (boundary.xMin) and max value (boundary.xMax)
  2. If your float is smaller than min value, it returns min value
  3. If your float is bigger than max value, it returns max value
  4. If your float is somewhere in between, it returns your float

In your case I would imagine it keeps your object position inside of some predefined boundaries. Basically, if it were to go outside of that boundary, it snaps the object back to the borders.