In Unity Shader often fill in a label with
Tags{ "LightMode" = "ForwardBase" "OnlyDirectional" ="True"}
Specify LightMode. As mentioned above, there are many types of LightMode. We are currently in mobile games, most of which are Forward pipelines. When I just started learning Unity ShaderLab, I was very confused why forward rendering is divided into two pipelines.
One is called ForwardBase and the other is called ForwardAdd
The official documentation of Unity explains these two differences, and do a small test to see if it is not.