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);
     }
 }