[skrebbel]

Your confusion stems from what kind of beginner the author means. You read it as "total beginner to anything vaguely related to microcontroller programmer". I assume the authors means it as "has programmed stuff with microcontrollers before but never made a hardware design from scratch yet". After all, picking a microcontroller is a design/architecture choice more than a programming choice.

[maxander]

Well, then there's another term he ought to define! :D I've done several projects using various flavours of Arduinos and Pis, but that sort of hobbyist-maker-level experience hasn't lead me to encounter an acronym for "Bill of Materials."

[wolf550e]

Few people have seriously contemplated ordering the manufacturing of a small run of something they themselves designed. More people have seen the term BOM when reading estimates of how much it costs big brands to manufacture a smartphone or a game console in industry publications or even in the more technically-oriented consumer reviews.