Shaderlab sample with notes in comment

Unity.shader

Shader "Unlit/UnityShader"
{
	Properties
	{
		_MainTex ("Texture", 2D) = "white" {}
	}
	SubShader
	{
		Tags { "RenderType"="Opaque" }
		LOD 100	//level of detail

		Pass
		{
			CGPROGRAM
			#pragma vertex vert	//define vertex function
			#pragma fragment frag	//define fragment function
			
			#include "UnityCG.cginc"	// some predefined helper function

			//	property data for vertex function, 
			//	which takes the shape of the model and modifies it
			struct appdata
			{
				float4 vertex : POSITION;	// x,y,z,w // [POSITION] tell shader we will use this for rendering
				float2 uv : TEXCOORD0;
			};

			//	property data for fragment function
			//	which applies color to the shape output by the vert function
			struct v2f
			{
				float2 uv : TEXCOORD0;
				float4 vertex : SV_POSITION;	// screen space position 
			};

			sampler2D _MainTex;
			float4 _MainTex_ST;

			v2f vert (appdata v)
			{
				v2f o;
				o.vertex = UnityObjectToClipPos(v.vertex);
				o.uv = TRANSFORM_TEX(v.uv, _MainTex);	//apply tiling and offset of texture
				return o;
			}
			
			fixed4 frag (v2f i) : SV_Target	// render target
			{
				// sample the texture
				fixed4 col = tex2D(_MainTex, i.uv);
				return col;
			}
			ENDCG
		}
	}
}