Check out example codes for "unity ongui button". It will help you in understanding the concepts better.

Code Example 1

// Draws 2 buttons, one with an image, and other with a text
// And print a message when they got clicked.using UnityEngine;
using System.Collections;public class ExampleClass : MonoBehaviour
    public Texture btnTexture;    void OnGUI()
        if (!btnTexture)
            Debug.LogError("Please assign a texture on the inspector");
        }        if (GUI.Button(new Rect(10, 10, 50, 50), btnTexture))
            Debug.Log("Clicked the button with an image");        if (GUI.Button(new Rect(10, 70, 50, 30), "Click"))
            Debug.Log("Clicked the button with text");

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