Sprites-Diffuse shader explained

Hello, I'm trying to learn shaders and though that It would be nice to study some of the built in unity shaders. Right now Im looking at the sprites diffuse shader. I'm really trying to understand but I really dont, where is the light coming from, I mean it says "Lighting off" and from what I can see it doesn't say anything about lighting. Can someone please explain the shader and tell me how the light works. Thanks!

 Shader "Sprites/Diffuse"
 {
     Properties
     {
         [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
         _Color ("Tint", Color) = (1,1,1,1)
         [MaterialToggle] PixelSnap ("Pixel snap", Float) = 0
     }
 
     SubShader
     {
         Tags
         { 
             "Queue"="Transparent" 
             "IgnoreProjector"="True" 
             "RenderType"="Transparent" 
             "PreviewType"="Plane"
             "CanUseSpriteAtlas"="True"
         }
 
         Cull Off
         Lighting Off
         ZWrite Off
         Blend One OneMinusSrcAlpha
 
         CGPROGRAM
         #pragma surface surf Lambert vertex:vert nofog keepalpha
         #pragma multi_compile _ PIXELSNAP_ON
         #pragma multi_compile _ ETC1_EXTERNAL_ALPHA
 
         sampler2D _MainTex;
         fixed4 _Color;
         sampler2D _AlphaTex;
 
         struct Input
         {
             float2 uv_MainTex;
             fixed4 color;
         };
         
         void vert (inout appdata_full v, out Input o)
         {
             #if defined(PIXELSNAP_ON)
             v.vertex = UnityPixelSnap (v.vertex);
             #endif
             
             UNITY_INITIALIZE_OUTPUT(Input, o);
             o.color = v.color * _Color;
         }
 
         fixed4 SampleSpriteTexture (float2 uv)
         {
             fixed4 color = tex2D (_MainTex, uv);
 
 #if ETC1_EXTERNAL_ALPHA
             color.a = tex2D (_AlphaTex, uv).r;
 #endif //ETC1_EXTERNAL_ALPHA
 
             return color;
         }
 
         void surf (Input IN, inout SurfaceOutput o)
         {
             fixed4 c = SampleSpriteTexture (IN.uv_MainTex) * IN.color;
             o.Albedo = c.rgb * c.a;
             o.Alpha = c.a;
         }
         ENDCG
     }
 
 Fallback "Transparent/VertexLit"
 }