He’s not wrong, all the descriptions and uses of all the material pins can be found in the ue4 docs.
"Emissive Color The Emissive Color input controls which parts of your Material will appear to glow because they are emitting light. Ideally, this will receive a masked texture (mostly black, except in the areas that need to glow).
Values greater than 1 are allowed because HDR lighting is supported."
Material Inputs in Unreal Engine | Unreal Engine 5.3 Documentation