Just a note - the solder mask is actually part of the PCB, in the past often green but now all sorts of colours. It covers up the tracks and copper fills etc. t

Just a note - the solder mask is actually part of the PCB, in the past often green but now all sorts of colours. It covers up the tracks and copper fills etc. that you don’t want solder on. What you’re referring to in the first paragraph is just called a stencil.