Instantiating Sprites

I'm trying to use prefabs to instantiate a sprite for a basic shooting setup however MonoDevelop gives me the error:

"The name 'playerShot' does not exist in the current context"

Here is my code:

 using UnityEngine;
 using System.Collections;
 
 public class PlayerControl : ShipClass
 {    
 
     void Start () 
     {
         //useless for now
     }
     
 
     void Update () 
     {
         if (Input.GetButtonDown ("Fire2")) 
         {
             Debug.Log ("Fire2 pressed!");
             Instantiate(playerShot);
         }
     }
 }

Where playerShot in this case is the prefab that I have created. I think I'm having trouble getting my head around how a script handles a prefab so any help on this matter would be appreciated. Thanks in advance.