Its from a youtube tutorial but the guy just glossed over this part and didn’t show the node being created. It looks like a make vector node but it has an extra yellow input pin above the xyz
Its just an add node with a vector input (yellow) 3 float inputs. You can right click the input node to change it’s type.
To identify the node look at the large symbol in the middle. In this case it’s “+”, so it’s add.
You can use the add pins button to add more inputs (by default it will have only 2 inputs)