MonoBehaviour in Unity

In Unity, most game objects are controlled using C# scripts. Almost every script you create manually inherits from the base class MonoBehaviour. This class enables Unity to manage object behavior: calling your code at game start, every frame, during collisions, and in other situations.

To create such a script:

1. In the Assets window, right-click
2. Select Create → MonoBehaviour Script
3. Give it a name, e.g., CSharpScript
4. Double-click it to open in the editor

You'll see a code template like this:

using UnityEngine;

public class CSharpScript : MonoBehaviour
{
    // Start is called once when the object starts
    void Start()
    {
        
    }

    // Update is called once per frame
    void Update()
    {
        
    }
}
  

using UnityEngine; — includes core Unity functionality.
public class CSharpScript : MonoBehaviour — creates a class with a name that must match the filename. Unity requires this for the script to work properly.

When the game starts, Unity calls Start() once, then automatically runs Update() every frame — this forms the core game loop.

In addition to these, Unity provides many other methods that get called at specific times — when the object is created, collides with something, gets enabled or disabled, etc. Below is a list of the most commonly used events that define a script’s lifecycle.