what does it mean when something does not exist in the current context mean

I am getting the error message of adjustcurrenthealth does not exist in this instance
here is the code if needed

			using System.Collections;

		 
		public class health : MonoBehaviour {
		       public GUIStyle PlayercurhealthplaceH;
		    public GUIStyle Playercurhealthtext;
		       public int MaxHealth = 320;
		    public int CurHealth = 320;
		    public float HealthBarLength;
		 
	 
	       void start(){
	 
	    HealthBarLength = 200; 
	 
	    }
	 
	    void OnGUI(){
	
	 
	    
				GUI.Box(new Rect((Screen.width /2) -339,(Screen.height /2) +300,200,20),"", PlayercurhealthplaceH);  
		
	       GUI.Box(new Rect((Screen.width /2) -339,(Screen.height /2) +300,200/(MaxHealth/CurHealth),20), CurHealth + "/" + MaxHealth, Playercurhealthtext);
	 
	    }
	 
	       public void AdjustCurrentHealth(int Adj){
	 
	       CurHealth += Adj;
	 
		       if (CurHealth <0)
		         CurHealth = 0;
	       if(CurHealth > MaxHealth)
	         CurHealth = MaxHealth;
	       if(MaxHealth < 1)
	         MaxHealth = 1;
	 
	       HealthBarLength = (200) * (CurHealth/(float)MaxHealth);
	 
	 
	 
	 
	    }
	 
	 
	    public void update() {
		adjustcurrenthealth(0);
	}
}

C# (and Javascript) is case sensitive. So your call on line 48 to ‘adjustcurrenthealth()’, is not the same as the function ‘AdjustCurrentHealth()’ on line 28.